Neural interfaces are entering an era where what once was science fiction is becoming a reality. As neural interfaces move out of the lab and into people's lives, the stability of neural decoding algorithms becomes ever more pressing. It is an unfortunate reality that neural implants degrade from long-term exposure to the neurological environment, however prior work has shown enhanced decoding stability in the application of 1D convolutional neural networks to neural feature extraction. However, these algorithms have high memory and processing requirements, prohibiting them from meeting the low area and power restrictions of implantable brain-machine interface decoding pipelines.
\r\n\r\nThis dissertation addresses the difficulties of implementing these algorithms on streamed neural data with high parallelism and low area and power costs. We address the unique dataflow characteristics of the feature extraction workload by designing a tailored processing element that reduces the memory access requirements by 2x. We further reduce system memory requirements through efficient process scheduling and memory partitioning. We then address the model complexity through retraining and analysis of the effect of various system parameters on the accuracy of kinematic decoding and hardware performance.
\r\n\r\nResults show that these design choices were able to successfully implement these intensive but performant algorithms within the power and area budgets of implantable devices. The architecture supports 192 channels that achieve state-of-the-art decoding stability at 1.8 uW and 12801 um^2 per channel in 65 nm CMOS technology. The device is a fully configurable, scalable, area and power efficient solution that supports models with 2-8 feature layers and a total kernel length of up to 256. This architecture reduces caching requirements by 5x over conventional computation schemes. We show our hardware optimized models maintain superior stability over time using recorded data from tetraplegic human participants with spinal cord injury. The models and hardware were validated in real time with a human subject in online closed-loop center-out cursor control experiments with micro-electrode arrays that were implanted for 6 years. Decoders using features generated with this work substantially improve the viability of long-term neural implants compared to other feature extraction methods currently present in low-power BMI hardware.
", "doi": "10.7907/40as-d020", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17856", "collection": "thesis", "collection_id": "17856", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02042026-041427925", "type": "thesis", "title": "Techniques Toward the Wafer-Scale Fabrication of Enzyme-Based Sensors", "author": [ { "family_name": "Smith", "given_name": "Richard Daniel", "orcid": "0000-0001-9384-105X", "clpid": "Smith-Richard-Daniel" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Roukes", "given_name": "Michael Lee", "orcid": "0000-0002-2916-6026", "clpid": "Roukes-M-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Wafer-scale fabrication of transducers directly on CMOS dies can minimize device size, increase the throughput and improve uniformity. Doing so with materials sensitive to the conditions encountered during typical microfabrication processes, such as enzymes, remains a challenge.
\r\n\r\nThis thesis investigates aspects of the performance and fabrication processes of electrochemical enzyme-based glucose-sensing transducers, intended for monolithic, implantable wireless sensors. The described work builds on past efforts in the Scherer group and focuses on the transducer fabrication compatible with CMOS wafers.
\r\n\r\nIn the first part, the pre-existing, enzyme-film lift-off patterning process is analyzed. The electrochemical processes of the three glucose oxidase-platinum electrodes are first investigated for the use in sensor diagnostics. The topography of the film is then related to the geometry of the patterns and to the performance of these transducers. Modifications are then made to reduce variation and improve yield. A process to optically profile such structures was also developed to better interpret the non-uniformity from thin film interference.
\r\n\r\nThe second part of this thesis describes the development and processing for plasma etch patterning the enzyme films. This aims to separate the uniformity of the film deposition from the definition of the boundaries, as occurs in many microfabrication processes with less sensitive materials. Strategies were developed that limit the optical, thermal, and chemical degradation of the enzyme activity. The resulting process demonstrated the feasibility of dry etch patterning functional enzyme films without loss of activity. Further, it clarified that improved structural uniformity can yield improved performance uniformity.
\r\n\r\nA final, tangential section investigates a positive tone electron beam lithography process that can be entirely performed in vacuum. Myo-inositol, an electron beam sensitive material, was unexpectedly found and refined. Dry processed negative tone resists avoid pattern collapse during wet development, but analogous positive-tone processes remain elusive. Myo-inositol films, deposited with thermal evaporation, were exposed with electron beams and then developed by subsequent heating. With dry etching and plasma stripping, the full dry process could be implemented in a vacuum cluster tool. While early in development and with challenges remaining, sub 100 nm features were transferred into an underlying thin metal film with this process.
", "doi": "10.7907/b6e8-ws51", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:18409", "collection": "thesis", "collection_id": "18409", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03092026-205538974", "type": "thesis", "title": "Human-Scale Ultrasound, Thermoacoustic, and Photoacoustic Tomography", "author": [ { "family_name": "Garrett", "given_name": "David Christopher", "orcid": "0000-0002-9747-8494", "clpid": "Garrett-David-Christopher" } ], "thesis_advisor": [ { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" } ], "thesis_committee": [ { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" }, { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Modern healthcare relies on imaging modalities that visualize internal anatomy and pathology. While X-ray computed tomography (CT) and magnetic resonance imaging (MRI) provide clinically useful imaging across many applications, they face significant barriers to more frequent use: ionizing radiation limits repeated CT scanning, and MRI\u2019s high cost and long acquisition times create access disparities. Conventional handheld ultrasonography enables rapid, low-cost imaging but remains limited by narrow fields of view, operator dependence, and challenging image interpretation. Photoacoustic tomography has emerged as a promising alternative that combines optical absorption contrast with acoustic detection, offering molecular specificity without ionizing radiation. However, conventional photoacoustic imaging remains limited to depths of several centimeters, inhibiting applications in deep-tissue imaging like gastrointestinal or whole-body assessment.
\r\n\r\nIn this thesis, we develop three approaches to extract clinically relevant information at human scales: ultrasound, thermoacoustic, and photoacoustic tomography. All three modalities leverage a custom 512-element, 60 cm diameter receiver array designed to detect acoustic signals across human-scale geometries. We validate these approaches through in vivo imaging, ex vivo tissue experiments, and phantom studies. First, we demonstrate ultrasound tomography of full human cross-sections in the abdomen and lower extremities, reconstructing backscatter contrast alongside quantitative maps of the speed of sound and attenuation coefficient. We show that ultrasound tomography enables visualization of features such as the liver, vasculature, muscle, and subcutaneous adipose across entire 2D human cross-sections. Second, we develop a thermoacoustic approach to guiding microwave ablation procedures. By modulating the microwave signal delivered through the probe, we record the generated thermoacoustic signals and use them to model the thermal dynamics during ablation. We show that this approach yields more accurate estimates of ablation zone geometry than standard look-up tables, which could allow for more precise ablation therapy. Third, we develop a method to extend the imaging depth of photoacoustic tomography using a wireless, ingestible capsule-based optical source. We demonstrate imaging depth up to 12 cm, which could open the door to photoacoustic imaging of regions like the gastrointestinal tract. Together, these approaches aim to expand the range of safe, informative, and accessible imaging modalities available to patients and clinicians.
", "doi": "10.7907/s8t2-qb10", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17778", "collection": "thesis", "collection_id": "17778", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11262025-191857258", "type": "thesis", "title": "An Experimental Characterization of Atmospheric Turbulence Effects on Millimeter Wave Propagation in a Controlled Environment", "author": [ { "family_name": "Sheng", "given_name": "Shawn JiaXiang", "orcid": "0009-0004-5478-7184", "clpid": "Sheng-Shawn-JiaXiang" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Elachi", "given_name": "Charles", "orcid": "009-0002-2156-967X", "clpid": "Elachi-C" }, { "family_name": "Cooper", "given_name": "Ken B.", "orcid": "0000-0001-9826-7157", "clpid": "Cooper-Kenneth-Brian" } ], "local_group": [ { "literal": "MICS Lab (Mixed Mode Integrated Circuits and Systems)" }, { "literal": "div_eng" } ], "abstract": "Atmospheric turbulence significantly affects electromagnetic (EM) wave propagation, especially at millimeter-wave (mmWave) frequencies, resulting in scintillation. Developing a statistical channel model to characterize these effects is crucial for accurate prediction and mitigation across various applications. In radar and satellite systems, turbulence can degrade signal quality and reduce accuracy. As telecommunications advance toward higher EM frequencies, turbulence will significantly influence signal performance. Moreover, statistical analysis of a propagating EM wave provides a unique opportunity for the remote sensing of atmospheric turbulence dynamics. The push towards an improved understanding of the planetary boundary layer on a global scale motivates the development of next generation measurement techniques.
\r\n\r\nThis thesis presents a novel approach for studying and characterizing the physical effects of atmospheric turbulence on mmWave propagation in a controlled laboratory environment. The method combines theoretical modeling and experimental validation to link meteorological parameters and turbulence dynamics to the scintillation effects on the power spectrum of a radio frequency (RF) signal. The experimental setup employs a versatile fan array wind tunnel to generate repeatable and controllable turbulent flows. A W-band (95GHz) transceiver is used to propagate EM energy through the turbulent flow, with the received signal analyzed to characterize the effects of turbulence-induced scintillation. Additional components include utility heaters for generating strong temperature gradients, a thermal screen and infrared camera to measure the temperature profile of the flow with high spatial resolution, a high-speed anemometer for turbulence spectrum characterization, and barometers and hygrometers for pressure and humidity measurements.
\r\n\r\nThe effects of temperature gradients and wind speeds are shown to increase and shift the power spectrum of the RF signal across multiple turbulent scales. Meteorological and RF measurements are directly linked through an empirical model that builds upon existing theoretical frameworks to accurately determine flow dynamics based on the characteristics of the received signal. The results are shown to be consistent and repeatable across multiple days, ambient conditions, and experimental configurations. Improvements and future directions are discussed, including extending this experimental setup to practical applications and leveraging the controllability to develop more sophisticated models that advance the understanding of scintillation.
", "doi": "10.7907/7sbc-5v10", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17769", "collection": "thesis", "collection_id": "17769", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11182025-233532194", "type": "thesis", "title": "Energy Efficient On-Chip Neural Feature Extraction for Brain-Computer-Interfaces", "author": [ { "family_name": "Bulfer", "given_name": "Steven Patrick", "orcid": "0000-0001-9942-1195", "clpid": "Bulfer-Steven-Patrick" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Pedroni", "given_name": "Volnei A.", "clpid": "Pedroni-Volnei-Antonio" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Neural interfaces are entering an era where what once was science fiction is becoming a reality. As neural interfaces move out of the lab and into people's lives, the stability of neural decoding algorithms becomes ever more pressing. It is an unfortunate reality that neural implants degrade from long-term exposure to the neurological environment, however prior work has shown enhanced decoding stability in the application of 1D convolutional neural networks to neural feature extraction. However, these algorithms have high memory and processing requirements, prohibiting them from meeting the low area and power restrictions of implantable brain-machine interface decoding pipelines.
\r\n\r\nThis dissertation addresses the difficulties of implementing these algorithms on streamed neural data with high parallelism and low area and power costs. We address the unique dataflow characteristics of the feature extraction workload by designing a tailored processing element that reduces the memory access requirements by 2x. We further reduce system memory requirements through efficient process scheduling and memory partitioning. We then address the model complexity through retraining and analysis of the effect of various system parameters on the accuracy of kinematic decoding and hardware performance.
\r\n\r\nResults show that these design choices were able to successfully implement these intensive but performant algorithms within the power and area budgets of implantable devices. The architecture supports 192 channels that achieve state-of-the-art decoding stability at 1.8 uW and 12801 um^2 per channel in 65 nm CMOS technology. The device is a fully configurable, scalable, area and power efficient solution that supports models with 2-8 feature layers and a total kernel length of up to 256. This architecture reduces caching requirements by 5x over conventional computation schemes. We show our hardware optimized models maintain superior stability over time using recorded data from tetraplegic human participants with spinal cord injury. The models and hardware were validated in real time with a human subject in online closed-loop center-out cursor control experiments with micro-electrode arrays that were implanted for 6 years. Decoders using features generated with this work substantially improve the viability of long-term neural implants compared to other feature extraction methods currently present in low-power BMI hardware.
", "doi": "10.7907/40as-d020", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:16751", "collection": "thesis", "collection_id": "16751", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09222024-230441454", "primary_object_url": { "basename": "HeatherLukas_PhDThesis.pdf", "content": "final", "filesize": 48618608, "license": "other", "mime_type": "application/pdf", "url": "/16751/1/HeatherLukas_PhDThesis.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Engineering Bioaffinity Sensors toward Continuous Electrochemical Biosensing", "author": [ { "family_name": "Lukas", "given_name": "Heather Lauren", "orcid": "0000-0002-8160-9066", "clpid": "Lukas-Heather-Lauren" } ], "thesis_advisor": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "thesis_committee": [ { "family_name": "Lester", "given_name": "Henry A.", "orcid": "0000-0002-5470-5255", "clpid": "Lester-H-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The rise of wearable sensing through smartwatches and continuous glucose monitors has made health data more widely accessible. Advances in machine learning have also been pivotal in identifying personalized health insights from biometric data streams. However, continuous biochemical data has been limited in sensor design by the availability of oxidoreductases (e.g., glucose oxidase, lactate dehydrogenase) to a given target. The challenge in engineering diverse oxidoreductase enzymes has led to the exploration of other generalized approaches to continuous electrochemical biosensing. To meet this need, we have explored a variety of bioaffinity sensing schemes using broad bioreceptor classes including antibodies, nucleic acids, and periplasmic binding proteins. We present a case study in electrochemical sensor design utilizing high-affinity antibodies for the rapid diagnosis of COVID-19 disease states. We then investigate the potential of nucleic acid-based electrochemical sensors for continuous sensing with a focus on structure-switching nucleic acid aptamers. The utility of aptamer sensors is demonstrated in the development of a serotonin aptamer sensor embedded in an ingestible capsule for continuous biosensing in the gastrointestinal tract. Applying the principles of electrochemical aptamer-based sensing, we explored the development of an electrochemical protein-based sensor for nicotine, which exploits the hinge-like binding motion of periplasmic binding proteins while also capitalizing on decades of protein evolution and characterization research. With the goal of continuous, noninvasive biochemical sensing, we evaluate the design considerations and translatability of these sensors for wearable sweat analysis. These biosensing techniques may enable the future hardware necessary to expand accessible biomedical data for the next wave of personalized health monitoring.", "doi": "10.7907/2c89-k924", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16551", "collection": "thesis", "collection_id": "16551", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07122024-082923823", "primary_object_url": { "basename": "Sekine_Ryoto_2024.pdf", "content": "final", "filesize": 106438025, "license": "other", "mime_type": "application/pdf", "url": "/16551/2/Sekine_Ryoto_2024.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Lithium Niobate Nanophotonic Circuits for Information Processing", "author": [ { "family_name": "Sekine", "given_name": "Ryoto", "orcid": "0000-0001-6135-8581", "clpid": "Sekine-Ryoto" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In today's world, electronic information processors are ubiquitous. This dissertation explores an alternative paradigm of processing information using nanophotonics. We develop and investigate nanophotonic lithium niobate circuits leveraging strong \u03c7\u207d\u00b2\u207e nonlinearity for information processing. We demonstrate promising performance of nanophotonic circuits as building blocks of unconventional computing architectures that exploit the rich classical and quantum dynamics inherent to optics. Additionally, we introduce a new class of ultrafast nanophotonic sources, enabling novel opportunities for information processing. Ultimately, this dissertation puts forth the building blocks of next generation ultrafast photonic information processors in lithium niobate nanophotonics which may lead to photonic advantage.", "doi": "10.7907/8vxv-eb34", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17428", "collection": "thesis", "collection_id": "17428", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06092025-053621987", "primary_object_url": { "basename": "Gray_Robert_2025.pdf", "content": "final", "filesize": 138129789, "license": "other", "mime_type": "application/pdf", "url": "/17428/1/Gray_Robert_2025.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Ultrafast Quadratic Nonlinear Dynamics and Soliton Formation in Parametric Amplifiers and Oscillators", "author": [ { "family_name": "Gray", "given_name": "Robert Matthew", "orcid": "0000-0001-5980-8774", "clpid": "Gray-Robert-Matthew" } ], "thesis_advisor": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In the more than 60 years since the invention of the laser, complementary developments in nonlinear and ultrafast optics have revolutionized fundamental science and technology, enabling the measurement of atomic and electronic motion at their native timescales, optical timekeeping with unprecedented precision, information processing offering speeds beyond those attainable in electronics, and novel spectroscopy and sensing techniques capable of parallel detection of several analytes with fast acquisition times and high sensitivity. On the one hand, pulsed sources are particularly well-suited for driving nonlinear phenomena, as the strength of nonlinear interaction depends on the peak power of the optical input. Conversely, spectral broadening, pulse shaping, and temporal sampling mechanisms enabled by nonlinearity have been critical in developing ultrafast sources and systems.
\r\n\r\nIn this thesis, we further explore this synergistic relationship between nonlinear and ultrafast optics. We specifically study nonlinear dynamical phenomena such as soliton formation and supercontinuum generation in parametric amplifiers and oscillators exhibiting a quadratic (χ(2)) nonlinearity, and we show how these processes can be leveraged for the efficient generation of ultrashort pulses and coherent broadband spectra, with direct application in sensing and information processing. We begin by exploring the formation of mid-infrared temporal simultons in a free-space optical parametric oscillator, and we exploit their formation dynamics for enhanced molecular sensing. Next, we turn to the thin-film lithium niobate platform and demonstrate pJ pulse energy, two-color soliton pulse compression to the two-cycle regime in a dispersion-engineered waveguide. We additionally show that the strong nonlinearity in such waveguides enables the on-chip characterization of ultrashort, ultra-weak pulses. Next, we demonstrate a coherent, multi-octave frequency comb from a far-above-threshold nanophotonic parametric oscillator and investigate the dynamics underpinning its formation. Finally, we show simultaneous oscillation of 70 independent time-multiplexed parametric oscillators in a dispersion-engineered nanophotonic cavity. Our results pave the way to a new generation of scalable and efficient ultrafast sources, sensors, and information processing systems powered by quadratic nonlinearity.
.", "doi": "10.7907/7zzq-4w69", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17212", "collection": "thesis", "collection_id": "17212", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05082025-224903418", "type": "thesis", "title": "A Path Towards Wearable Affective General Intelligence", "author": [ { "family_name": "Solomon", "given_name": "Samuel Aaron", "orcid": "0000-0001-7199-6659", "clpid": "Solomon-Samuel-Aaron" } ], "thesis_advisor": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Anandkumar", "given_name": "Anima", "orcid": "0000-0002-6974-6797", "clpid": "Anandkumar-A" }, { "family_name": "Perona", "given_name": "Pietro", "orcid": "0000-0002-7583-5809", "clpid": "Perona-P" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Artificial intelligence continues to support our daily decision-making tasks yet remains disconnected from our dynamic emotions driving these behaviors. Wearable technologies can supplement interactions with continuous emotion biofeedback, but existing models struggle to generalize across emerging biomarkers, platforms, and affective expressions. Here, we introduce a meta-analysis into embedding concurrent fragmented biosignals across 15 medical platforms, spanning five bodily locations, within a single profile that enables efficient and generalizable downstream affective analysis. We achieved this through a Lie manifold neural architecture that simultaneously reconstructs over 118,000 missing biometric details in 205 biomarkers and accurately forecasts 100 affective states across cohorts, questionnaires, and activities. We validated this framework across five datasets to propose a new skin-conformal, soft bioelectronic, affective computing platform that demonstrates closed-loop emotion modulation within thermal, audio, and visual interventions delivered through virtual, holographic, and conversational agents. Our framework establishes a new foundational bidirectional architecture for scalable, interpretable, and emotionally intelligent human-computer interactions.", "doi": "10.7907/2s0x-qq57", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17343", "collection": "thesis", "collection_id": "17343", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06012025-202413304", "primary_object_url": { "basename": "CChoi_Thesis_Final.pdf", "content": "final", "filesize": 59635106, "license": "other", "mime_type": "application/pdf", "url": "/17343/1/CChoi_Thesis_Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Techniques for Molecular Detection: From Mid-Infrared Spectrometers to Nanopore Devices", "author": [ { "family_name": "Choi", "given_name": "Changsoon", "orcid": "0009-0005-4037-8643", "clpid": "Changsoon-Changsoon" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Petillo", "given_name": "Peter A.", "orcid": "0000-0001-7516-2221", "clpid": "Petillo-Peter-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents the development and characterization of three distinct molecular detection platforms aimed at improving accessibility and scalability. These systems utilize optical and electrical sensing techniques to analyze solid, liquid, and gas-phase samples, addressing challenges in portability, cost-effectiveness, and throughput.
\r\n\r\nFirst, a compact mid-infrared spectrometer was developed using a continuously variable filter composed of Ge/BaF2 distributed Bragg reflectors and a 2-D microbolometer array. This design enables high signal-to-noise ratio measurements across the long-wave infrared region (7.5 - 10.5 \u00b5m) without requiring moving parts. The system was calibrated using polymer samples and validated through spectral measurements of gases and liquids using gas cells and attenuated total reflection configurations. The results demonstrate good agreement with commercial Fourier transform infrared (FTIR) spectrometers while maintaining a significantly smaller form factor and lower cost.
\r\n\r\nNext, a tunable diode laser absorption spectroscopy system was implemented for methane detection. The system uses wavelength-modulated distributed feedback lasers and lock-in detection to achieve high sensitivity. Both free-space and fiber-optic configurations were developed, with detection limits down to 0.5 ppm-m for the free-space system. Real-time gas monitoring was demonstrated using retroreflectors and beam-steering optics, enabling multi-point detection with a single source-detector pair.
\r\n\r\nFinally, a design for a multiplexed nanopore detector was proposed to improve throughput. Electric properties of solid-state nanopores were investigated through analytical modeling, numerical simulations, and experimental conductance measurements. A new sensing architecture incorporating embedded electrodes was introduced. Simulations confirmed that this design enables independent detection of translocation events at each pore. Prototype devices were fabricated to validate the concept.
\r\n\r\nTogether, these platforms offer scalable and accessible alternatives to conventional molecular detection systems, with potential applications in environmental monitoring, industrial gas sensing, and real-time molecular diagnostics.
", "doi": "10.7907/82w6-ka57", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16167", "collection": "thesis", "collection_id": "16167", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08282023-193415593", "type": "thesis", "title": "Adaptive Optoelectronic Systems: From Bio- Sensing to Free-Space Optical Communication", "author": [ { "family_name": "Aghlmand", "given_name": "Fatemeh", "orcid": "0000-0002-5103-9314", "clpid": "Aghlmand-Fatemeh" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Murray", "given_name": "Richard M.", "orcid": "0000-0002-5785-7481", "clpid": "Murray-R-M" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Mirhosseini", "given_name": "Mohammad", "orcid": "0000-0002-9084-6880", "clpid": "Mirhosseini-M" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "MICS Lab (Mixed Mode Integrated Circuits and Systems)" }, { "literal": "div_eng" } ], "abstract": "Portable and point-of-care medical devices are becoming an essential part of today\u2019s medical technology. An affordable personal device that can diagnose and monitor a medical condition in real-time will improve the patient\u2019s life quality in many ways. Additionally, by autonomously providing the suitable treatment, a universal healthcare device can be accessible to most of the population at a low cost. Despite considerable efforts and great outcomes, most of the prior arts in realizing these devices have limitations that hinder their widespread use in portable applications. On the other hand, comprehensive environmental sensing has drawn great attention in the last few years. Monitoring the quality of water, soil, air, and waste is of utmost importance to study their effect on human life and also to recognize the consequence of human actions on the planet.
\r\n\r\nThe most important factors in developing a compact and portable device for medical and environmental applications are their integration level, ease of use with biomarkers, and reliability of the results. Detecting a specific chemical in the biology world relies on a biochemical reaction with a transducer that can convert the resulting signal into a measurable signal in various modalities, such as electrical, magnetic, or optical. Hence, the biosensing device is often a multidisciplinary apparatus that is not readily integrable due to the need for miniaturizing otherwise bulky optical or magnetic components. The key requirement in device miniaturization, though, is to use standard technologies to avoid extra cost and processing time for the device\u2019s mass production. The path towards achieving such a device needs revisiting the existing solutions and the capabilities of the powerful yet affordable CMOS technologies to seamlessly integrate various device components, namely electronics, biology, and optics/magnetics. This dissertation provides an overview of integrated biosensors and presents novel designs in optics and electronics to implement a fully integrated and miniaturized device for medical and environmental applications.
\r\n\r\nFluorescence sensing is one of the most reliable and widespread detection methods with well- established tools in synthetic biology. Specifically, bacterial-based fluorescence sensors offer unsurpassed advantages to labeled detection since bacterial cells, when engineered, can respond to various elements in their surroundings at a low cost and quite efficiently. The use of live bacterial cells is also of great importance in establishing the bidirectional link with the CMOS device. By monitoring the dynamics of the cells\u2019 growth and their protein expression, a desired biology response can be initiated upon receiving the stimulating signal from the device. The conventional methods in fluorescence sensing involve an elaborate setup with many external optical components unsuitable for portable and in vivo applications. Hence, integrating silicon chips and live bacterial biosensors in a miniaturized \"Silicon-Cell\" system can enable a wide range of applications for both sensing and remediation. Such integrated systems need on-chip optical filtering in the wavelength range compatible with fluorescent proteins, which are widely used signal reporters for bacterial biosensors.
\r\n\r\nIn the first part of this dissertation, we introduce a fully integrated fluorescence sensor in 65nm standard CMOS process comprising on-chip bandpass optical filters, photodiodes, and processing circuitry. The metal/dielectric layers in CMOS are employed to implement low- loss cavity-type optical filters, achieving a bandpass response at 600/700nm range suitable to work with fluorescent proteins. The sensitivity of the sensor is further improved in the electrical domain by using a C-TIA with variable switched capacitor gain, a voltage- controlled current source (VCCS), and feedback-controlled low-leakage switches, resulting in a minimum measured current of 1.05fA with SNR >18dB. The sensor can measure the statics/dynamics of the fluorescence signal as well as the growth of living E. coli bacterial cells. Using a differential design and layout, the sensor can distinguish two biochemical signals by measuring two fluorescent proteins encoded in a single bacterial strain. Furthermore, a proof of concept is demonstrated to establish bidirectional communication between living cells and the CMOS chip, using a fluorescent protein regulated by an optogenetic control.
\r\n\r\nIn the second part of this dissertation, we describe a fully integrated high-bandwidth optical receiver for RF-over-free-space optics (RoFSO). This work is motivated by the availability of a wide, unregulated bandwidth at the optical frequencies and the lower cost and setup time due to using atmosphere instead of fiber optics as the communication channel. Nonetheless, the atmospheric link poses serious challenges, including severe beam intensity and phase distortions. Here we present novel solutions at the system and circuit level to make the receiver adaptive and resilient to the mentioned distortions. The chip is designed and implemented in a 28nm CMOS process, and it is shown to achieve a measured gain of 58dB and bandwidth of 18GHz. The link performance is assessed by exposing the system to more than 26dB of optical loss, equivalent to 3.5km of free space distance under moderate visibility conditions. For a proof-of-concept demonstration, an 8Gbps non-coherent DPSK signal with an RF bandwidth of 10GHz is transmitted, resulting in a BER of 1 \u00d7 10\u207b\u2074 for a minimum received power of -30dBm and while consuming 19.2mW power at the receiver.
", "doi": "10.7907/hj19-7516", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16239", "collection": "thesis", "collection_id": "16239", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11062023-050222447", "type": "thesis", "title": "Wearable Sweat Sensors for Disease Monitoring and Management", "author": [ { "family_name": "Tu", "given_name": "Jiaobing", "orcid": "0000-0002-7653-6640", "clpid": "Tu-Jiaobing" } ], "thesis_advisor": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "thesis_committee": [ { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Dabiri", "given_name": "John O.", "orcid": "0000-0002-6722-9008", "clpid": "Dabiri-J-O" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "With the emphasis of healthcare shifting towards prevention and early detection of diseases and monitoring of chronic conditions, there is a growing need for hassle\u2010free telemedicine sensor technologies that can be seamlessly integrated into daily life. While significant progress has been made in the development of wearable sweat and salivary biosensors to meet this need for rapid, real-time collection of physiological information, the majority of current epidermal sensing systems are unable to detect trace-level disease-relevant biomarkers accurately in biofluids and cannot be mass produced. To meet this demand for low-cost, mass-producible mHealth devices for at-home settings, we developed several fully integrated laser-engraved graphene-based biosensors for the detection of low-concentration sweat and saliva analytes including hormones (cortisol) and proteins (C-reactive protein). Several graphene surface engineering strategies are investigated for the sensitive and selective detection of targets. System-level engineering and microfluidic designs are explored to achieve on-demand sweat induction and harvesting under sedentary settings and automated sweat and reagent routing and in situ signal correction and analysis for facile operation on the skin. The utility of these fully integrated flexible mHealth systems is evaluated through multiple human studies involving healthy and various patient subgroups towards stress assessment, as well as the monitoring and management of various chronic conditions including chronic obstructive pulmonary disease, heart failure, and inflammatory bowel diseases. These fully integrated mHealth devices demonstrate a technology that can be easily adapted to monitor a broad spectrum of disease-specific proteins, cytokines, and hormones, thus advancing future applications in personalized disease diagnosis, management, and prevention.", "doi": "10.7907/7jdg-z479", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16255", "collection": "thesis", "collection_id": "16255", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12052023-185529151", "primary_object_url": { "basename": "Thesis - Jihong Min.pdf", "content": "final", "filesize": 9341850, "license": "other", "mime_type": "application/pdf", "url": "/16255/11/Thesis - Jihong Min.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Innovations in Wireless Bioelectronics for Precision Medicine, from Sustainable Sweat Sensing to Ingestible Gut Monitoring", "author": [ { "family_name": "Min", "given_name": "Jihong", "orcid": "0000-0002-5788-1473", "clpid": "Min-Jihong" } ], "thesis_advisor": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" }, { "family_name": "Lester", "given_name": "Henry A.", "orcid": "0000-0002-5470-5255", "clpid": "Lester-H-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Biofluids, constituting about 60% of the human body, serve as treasure troves of biomarkers such as metabolites and electrolytes, shedding light on individual health conditions. Although blood and urine tests have been routinely utilized, they are limited by their invasive and episodic nature. However, the promise of continuous and noninvasive access to other biofluids like sweat, GI fluids, and saliva paves the way for real-time, onsite health monitoring. This thesis delves into the untapped potential of wearable sensors and noninvasive biofluid analysis, emphasizing the importance of continuous and sustainable monitoring for predictive personal healthcare. Chapter 1 introduces the paradigm of biofluid sensing, focusing on sweat as a key candidate for personalized healthcare applications. Chapter 2 delves into the physiology of sweat glands, highlighting the composition of sweat and the mechanisms behind sweat extraction, either through natural exercise or iontophoretic stimulation. Chapter 3 embarks on the development of innovative sensors designed for detecting clinically pertinent biomarkers in sweat, a step forward in predictive health analytics. In Chapter 4, the spotlight is on system integration, as the study emphasizes the need for miniaturized and reliable wireless sensor devices that ensure minimal discomfort and maximum reliability. Chapters 5 and 6 delve into strategies for sustainably powering wearable devices from energy harvested from body motions and from ambient light, respectively. The final chapter, Chapter 7, extrapolates the aforementioned technologies for the realm of ingestible devices, adapting them for electrochemical sensing in alternate media, primarily gastrointestinal fluids. This allows for enhanced detection of gastrointestinal diseases and a deeper understanding of the intricate gut-brain axis. The ultimate vision of this research is to equip individuals with wearable and ingestible sensors that can seamlessly monitor a broad spectrum of clinically relevant biomarkers. This continuous monitoring, coupled with data analytics, will potentially catalyze a shift from reactive to predictive healthcare, ushering in an era of personalized therapeutic interventions. As wearable sweat and ingestible sensors become mainstream, a confluence of biosensing mechanisms, materials science, and flexible electronics is anticipated enable continuous and unobtrusive acquisition of clinically relevant biomarkers over prolonged periods and large populations, further refining the nexus between health monitoring and precision medicine.", "doi": "10.7907/kcm7-wz71", "publication_date": "2024-06-14", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16344", "collection": "thesis", "collection_id": "16344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04072024-202335451", "type": "thesis", "title": "Energy-Efficient and Robust Algorithms for Biomedical Applications", "author": [ { "family_name": "Haghi", "given_name": "Benyamin Allahgholizadeh", "orcid": "0000-0002-4839-7647", "clpid": "Haghi-Benyamin-Allahgholizadeh" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Andersen", "given_name": "Richard A.", "orcid": "0000-0002-7947-0472", "clpid": "Andersen-R-A" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Medical devices play a critical role in improving the quality of life for patients and assisting physicians by monitoring, detecting, and helping manage chronic conditions such as epilepsy and spinal cord injuries. To perform these functions effectively, these devices must extract the most relevant information from complex medical data. However, the functionality of these medical devices has been limited by the existing challenges in medical applications. Some of these challenges include the complexity in the analysis of raw medical data, adaptability, non-stationarity, noise, large data volumes, real-time processing, limited resources, and high accuracy demands. Moreover, considering factors such as individual differences, environmental influences, and genetic variations, medical data will cause numerous variations and uncertainties in analyzing and interpreting the medical conditions in different biomedical applications. Medical data analysis is already complex and is further complicated by issues like non-stationarity and noise, especially when using traditional and manual methods. When it comes to the designing, implementation, and utilization of wearable and implantable medical devices, efficiency, accuracy, and adaptability become crucial. Particularly, applications that require fast control of equipment, such as brain-machine interfaces (BMIs), make the need for fast decision-making evident. Medical data have been conventionally managed by reliance on extensive manual labor. However, such manual data management techniques are not scalable, have inefficient procedures, and are more likely to produce errors. Therefore, more advanced, automated methods are required immediately considering the existing challenges of the current medical data analysis techniques.
\r\n\r\nSuch a shift in data processing and management will lead to more trustable procedures that can significantly improve the accuracy and efficiency of medical data analysis. Other than being just an improvement, such transformation signifies a noteworthy point in the development of medical devices. In this view, it is essential to introduce advanced technology and novel methods for medical data processing as well as automation. Therefore, it becomes critical that these high-performance and advanced techniques can efficiently be implemented with minimum effects on hardware for clinical applications. Currently, artificial intelligence (AI) and its subfield machine learning (ML) has led to major transformations in designing and utilization of various medical devices. Among all these biomedical applications, three major area are addressed in this thesis: Brain Machine Interfaces (BMIs), seizure detection, and classification of arrhythmias in cardiac rhythms. We selected these three applications due to their significance and ability to improve patient treatment further. Additionally, we showed how we used machine learning algorithms for each of these applications to address their current challenges.
\r\n\r\nIn our work related to Brain-Machine Interfaces (BMIs), we have been focused on improving the quality of life for individuals with spinal cord injury (SCI) through two studies. In our initial study, we have designed and implemented a deep multi-state Dynamic Recurrent Neural Network (DRNN) decoder for BMI applications. This algorithm decodes neural data recorded from the posterior parietal cortex (PPC) and the motor cortex (M1) of human participants to appropriate control signals to predict computer cursor kinematics on the computer screen. By reducing the amount of history used in predicting the movement kinematics from the recorded neural data, we have demonstrated that improved performance and robustness are preserved while memory and power consumption are reduced. We then compared the performance of DRNN with other decoding techniques to demonstrate that when operating on wavelet-based neural features, our proposed DRNN-based decoder outperforms other decoding techniques. Therefore, DRNN have the potential to be used for more efficient and effective BMIs. After developing DRNN as a decoding technique for BMI applications, we have implemented an efficient feature extraction technique, referred to as Feature Extraction Network (FENet), which has been designed by using convolutional neural networks for optimizing feature extraction and decoding to ensure consistency across electrodes when decoding the recorded neural data to the movement kinematics in BMI systems. After being tested with data recorded from the posterior parietal and motor cortices of three human participants, FENet outperformed existing feature extraction techniques such as threshold crossings and wavelet transforms, and it significantly enhanced both closed- and open-loop cursor controls. We have also evaluated the generalizability of FENet when applied to different datasets, brain regions, and participants. Therefore, the results of our research in BMI technology have the potential to promise the improvement of the quality of life for spinal cord injury (SCI) patients.
\r\n\r\nSecond, we co-designed EKGNet, a convolutional network that combines analog computing and deep learning for detecting heartbeat arrhythmia. EKGNet demonstrated high accuracy while minimizing power consumption, effectively overcoming challenges related to analog circuitry and real-time processing. The experimental findings, using PhysionNet\u2019s MIT-BIH and PTB Diagnostics datasets, showed an average balanced accuracy of 95% for intra-patient arrhythmia classification and 94.25% for myocardial infarction (MI) classification.
\r\n\r\nFinally, we designed a real-time seizure detector by using XGboost as a technique relies on gradient boosted trees, which can help with the fast and accurate diagnosis of seizure for epileptic patients. With an averaged detection latency of 1.1 seconds, this design attained average F1 scores of 99.23% and 87.86% under various data splitting methods. The energy-area-latency product was 27\u00d7 lower than the current state-of-the-art solutions, which allowed for adjustments that were specific to each patient and significantly reduced energy consumption.
\r\n\r\nThe results presented in this dissertation demonstrate the potential of AI in addressing the existing challenges in three biomedical applications: brain-machine interfaces (BMI), seizure detection, and heartbeat arrhythmia detection. By addressing these existing challenges including complex biological data management, real-time processing constraints, and limited resources in biomedical applications, AI has the potential to improve the quality of life for patients suffering from neurological disorders and medical conditions. Moreover, the improved precision, operational efficiency, and flexibility caused by the integration of AI into the design of the future biomedical systems will potentially assist healthcare providers to offer enhanced support and treatment to patients. While we have focused on the three above-mentioned biomedical applications, the principles learned from our analysis may be relevant and can be extended to other biomedical applications.
", "doi": "10.7907/gkx4-s019", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16344", "collection": "thesis", "collection_id": "16344", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04072024-202335451", "type": "thesis", "title": "Energy-Efficient and Robust Algorithms for Biomedical Applications", "author": [ { "family_name": "Haghi", "given_name": "Benyamin Allahgholizadeh", "orcid": "0000-0002-4839-7647", "clpid": "Haghi-Benyamin-Allahgholizadeh" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" }, { "family_name": "Andersen", "given_name": "Richard A.", "orcid": "0000-0002-7947-0472", "clpid": "Andersen-R-A" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Medical devices play a critical role in improving the quality of life for patients and assisting physicians by monitoring, detecting, and helping manage chronic conditions such as epilepsy and spinal cord injuries. To perform these functions effectively, these devices must extract the most relevant information from complex medical data. However, the functionality of these medical devices has been limited by the existing challenges in medical applications. Some of these challenges include the complexity in the analysis of raw medical data, adaptability, non-stationarity, noise, large data volumes, real-time processing, limited resources, and high accuracy demands. Moreover, considering factors such as individual differences, environmental influences, and genetic variations, medical data will cause numerous variations and uncertainties in analyzing and interpreting the medical conditions in different biomedical applications. Medical data analysis is already complex and is further complicated by issues like non-stationarity and noise, especially when using traditional and manual methods. When it comes to the designing, implementation, and utilization of wearable and implantable medical devices, efficiency, accuracy, and adaptability become crucial. Particularly, applications that require fast control of equipment, such as brain-machine interfaces (BMIs), make the need for fast decision-making evident. Medical data have been conventionally managed by reliance on extensive manual labor. However, such manual data management techniques are not scalable, have inefficient procedures, and are more likely to produce errors. Therefore, more advanced, automated methods are required immediately considering the existing challenges of the current medical data analysis techniques.
\r\n\r\nSuch a shift in data processing and management will lead to more trustable procedures that can significantly improve the accuracy and efficiency of medical data analysis. Other than being just an improvement, such transformation signifies a noteworthy point in the development of medical devices. In this view, it is essential to introduce advanced technology and novel methods for medical data processing as well as automation. Therefore, it becomes critical that these high-performance and advanced techniques can efficiently be implemented with minimum effects on hardware for clinical applications. Currently, artificial intelligence (AI) and its subfield machine learning (ML) has led to major transformations in designing and utilization of various medical devices. Among all these biomedical applications, three major area are addressed in this thesis: Brain Machine Interfaces (BMIs), seizure detection, and classification of arrhythmias in cardiac rhythms. We selected these three applications due to their significance and ability to improve patient treatment further. Additionally, we showed how we used machine learning algorithms for each of these applications to address their current challenges.
\r\n\r\nIn our work related to Brain-Machine Interfaces (BMIs), we have been focused on improving the quality of life for individuals with spinal cord injury (SCI) through two studies. In our initial study, we have designed and implemented a deep multi-state Dynamic Recurrent Neural Network (DRNN) decoder for BMI applications. This algorithm decodes neural data recorded from the posterior parietal cortex (PPC) and the motor cortex (M1) of human participants to appropriate control signals to predict computer cursor kinematics on the computer screen. By reducing the amount of history used in predicting the movement kinematics from the recorded neural data, we have demonstrated that improved performance and robustness are preserved while memory and power consumption are reduced. We then compared the performance of DRNN with other decoding techniques to demonstrate that when operating on wavelet-based neural features, our proposed DRNN-based decoder outperforms other decoding techniques. Therefore, DRNN have the potential to be used for more efficient and effective BMIs. After developing DRNN as a decoding technique for BMI applications, we have implemented an efficient feature extraction technique, referred to as Feature Extraction Network (FENet), which has been designed by using convolutional neural networks for optimizing feature extraction and decoding to ensure consistency across electrodes when decoding the recorded neural data to the movement kinematics in BMI systems. After being tested with data recorded from the posterior parietal and motor cortices of three human participants, FENet outperformed existing feature extraction techniques such as threshold crossings and wavelet transforms, and it significantly enhanced both closed- and open-loop cursor controls. We have also evaluated the generalizability of FENet when applied to different datasets, brain regions, and participants. Therefore, the results of our research in BMI technology have the potential to promise the improvement of the quality of life for spinal cord injury (SCI) patients.
\r\n\r\nSecond, we co-designed EKGNet, a convolutional network that combines analog computing and deep learning for detecting heartbeat arrhythmia. EKGNet demonstrated high accuracy while minimizing power consumption, effectively overcoming challenges related to analog circuitry and real-time processing. The experimental findings, using PhysionNet\u2019s MIT-BIH and PTB Diagnostics datasets, showed an average balanced accuracy of 95% for intra-patient arrhythmia classification and 94.25% for myocardial infarction (MI) classification.
\r\n\r\nFinally, we designed a real-time seizure detector by using XGboost as a technique relies on gradient boosted trees, which can help with the fast and accurate diagnosis of seizure for epileptic patients. With an averaged detection latency of 1.1 seconds, this design attained average F1 scores of 99.23% and 87.86% under various data splitting methods. The energy-area-latency product was 27\u00d7 lower than the current state-of-the-art solutions, which allowed for adjustments that were specific to each patient and significantly reduced energy consumption.
\r\n\r\nThe results presented in this dissertation demonstrate the potential of AI in addressing the existing challenges in three biomedical applications: brain-machine interfaces (BMI), seizure detection, and heartbeat arrhythmia detection. By addressing these existing challenges including complex biological data management, real-time processing constraints, and limited resources in biomedical applications, AI has the potential to improve the quality of life for patients suffering from neurological disorders and medical conditions. Moreover, the improved precision, operational efficiency, and flexibility caused by the integration of AI into the design of the future biomedical systems will potentially assist healthcare providers to offer enhanced support and treatment to patients. While we have focused on the three above-mentioned biomedical applications, the principles learned from our analysis may be relevant and can be extended to other biomedical applications.
", "doi": "10.7907/gkx4-s019", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16109", "collection": "thesis", "collection_id": "16109", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06122023-184556858", "primary_object_url": { "basename": "Thesis - Arian Hashemi Talkhooncheh - 2022.pdf", "content": "final", "filesize": 10208379, "license": "other", "mime_type": "application/pdf", "url": "/16109/1/Thesis - Arian Hashemi Talkhooncheh - 2022.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Holistic Design in High-Speed Silicon Photonics and Low-Power Electronics Platforms", "author": [ { "family_name": "Hashemi Talkhooncheh", "given_name": "Arian", "orcid": "0000-0001-8946-5047", "clpid": "Hashemi-Talkhooncheh-Arian" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" }, { "family_name": "Zilkie", "given_name": "Aaron", "orcid": "0000-0002-4114-2297", "clpid": "Zilkie-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "High-speed interconnects are of vital importance to the operation of high-performance computing and communication systems, determining the ultimate bandwidth or data rates at which the information can be exchanged. Optical interconnects and the employment of high order modulation formats are considered as the solutions to fulfilling the envisioned speed and power efficiency of future interconnects. One area of growing importance in optical interconnects is the design and optimization of energy-efficient transmitters with superior power efficiency. Enhancing the electro-optical bandwidth density while keeping the power efficiency optimized, requires improvement in the optical power penalty of photonic integrated circuits. Moreover, co-optimization of electronics and photonics enables a path towards sub-pJ/b transmission efficiency. In this dissertation, architectural and circuit-level energy-efficient techniques serving these goals are presented.\r\n\r\nFirst, an integrated DAC-less PAM-4 transmitter in a multi-micron silicon photonics platform using 2 binary-driven uneven-length SiGe EAMs in an unbalanced MZI is presented. The optical transmitter exhibits 5.5dB ER at 100 Gb/s with 2.1dB SNR improvement compared to single EAMs driven by PAM-4 signals. Also, A DAC-less 200Gb/s QAM-16 transmitter in a multi-micron silicon-photonics platform using 4 binary-driven SiGe EAMs in an unbalanced MZI is presented. The transmitter exhibits bit-error rates of 3\u00d710-4 and 2.8\u00d710-4 for square and hexagonal constellations.\r\n\r\nSecond, a 100Gb/s PAM4 optical transmitter system implemented in a 3D-integrated Silicon Photonics-CMOS platform is presented. The photonics chip includes a push-pull segmented Mach-Zehnder Modulator (MZM) structure using highly capacitive (415fF to 1.1pF), yet optically efficient (V\u03c0L= 0.8 V.cm) metal-oxide-silicon capacitor (MOSCAP) phase modulators. Two pairs of U-shaped modulator segments with effective lengths of 170\u00b5m and 450\u00b5m are driven at 50 Gbaud by a dual-channel 28nm CMOS driver, which is flip-chip bonded to the photonics chip. The driver cores utilize digitally controllable pre-distortion and inductive peaking to achieve sufficient electro-optical bandwidth. The drivers deliver 1.2Vppd swing to modulators using a 0.9V supply and on-chip serializers that generate 50Gb/s data streams. The electronics chip consumes 240mW achieving 2.4pJ/bit energy efficiency. The overall electro-optical bandwidth (EOBW), without any pre-distortion, is increased by approximately 56% and 48% for the 170\u00b5m and 450\u00b5m segments, respectively, when compared to their EOBW measured by 65GHz 50-Ohm terminated probes. The optical input power to the photonics chip is +10dBm and an erbium-doped fiber amplifier amplifies output signals by 11dB. The 50Gb/s NRZ optical raw eye diagram exhibits 4.3dB extinction ratio (ER) and 1.2dBm of optical modulation amplitude (OMA). The 100Gb/s PAM4 optical raw eye diagram shows 4.3dB ER and 1.4dBm OMA with a transmitter dispersion eye closure quaternary (TDECQ) of 1.53dB after a 5-tap feed-forward-equalization (FFE) filter. The PAM4 TDECQ changes by 53% when the temperature is increased from 30\u00baC to 90 \u00baC at the optimum forward bias voltage of 1V.\r\n\r\nThird, an efficient cold-starting energy harvester system, fabricated in 65nm CMOS is presented. The proposed harvester uses no external electrical components and is compatible with biofuel-cell voltage and power ranges. A power-efficient system architecture is proposed to keep the internal circuitry operating at 0.4V while regulating the output voltage at 1V using switched-capacitor DC-DC converters and a hysteretic controller. A startup enhancement block is presented to facilitate cold startup with any arbitrary input voltage. A real-time on-chip 2D maximum power point tracking with source degradation tracing is also implemented to maintain power efficiency maximized over time. The system performs cold startup with a minimum input voltage of 0.39V and continues its operation if the input voltage degrades to as low as 0.25V. Peak power efficiency of 86% is achieved at 0.39V of input voltage and 1.34\u03bcW of output power with 220nW of average power consumption of the chip. The end-to-end power efficiency is kept above 70% for a wide range of loading powers from 1\u03bcW to 12\u03bcW. The chip is integrated with a pair of lactate biofuel-cell electrodes with 2mm of diameter on a prototype printed circuit board (PCB). Integrated operation of the chip with the electrodes and a lactate solution is demonstrated.", "doi": "10.7907/8yj9-2a62", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:16066", "collection": "thesis", "collection_id": "16066", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022023-215651797", "type": "thesis", "title": "Advancements in Hemodynamic Measurement: Arterial Resonance, Ultrasound, and Machine Learning", "author": [ { "family_name": "Yurk", "given_name": "Dominic Jeffrey", "orcid": "0000-0002-2276-4189", "clpid": "Yurk-Dominic-Jeffrey" } ], "thesis_advisor": [ { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "thesis_committee": [ { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Rajagopal", "given_name": "Aditya", "orcid": "0000-0002-7768-2463", "clpid": "Rajagopal-Aditya" }, { "family_name": "Abu-Mostafa", "given_name": "Yaser S.", "clpid": "Abu-Mostafa-Y-S" } ], "local_group": [ { "literal": "3MT Competition (Caltech)" }, { "literal": "div_eng" } ], "abstract": "This thesis covers two separate projects which both use ultrasound to measure a form of blood pressure in very different ways. The first project focuses on the noninvasive measurement of continuous arterial blood pressure via the previously unstudied phenomenon of arterial resonance. While prior research efforts have attempted many methods of noninvasive blood pressure measurement, none has been able to generate continuous, calibration-free measurements based on a first-principles physical model. This work describes the derivation of this resonance-based model, its in vitro validation, and its in vivo testing on 60 subjects. This testing resulted in robust resonance detection and accurate calculation of BP in the large majority of evaluated subjects, representing very promising performance for the first test of a new biomedical technology. The second study changes focus to the measurement of blood pressure in the right atrium of the heart, an important clinical indicator in heart disease patients. Rather than developing a new physical approach, this project used machine learning to model the existing assessments made by cardiologists. Comparison to gold standard invasive catheter measurements showed that model predictions were statistically indistinguishable from cardiologist measurements. Both of these projects represent significant advances in expanding precise blood pressure measurements beyond critical care units and expanding access to a much broader population.
", "doi": "10.7907/q7j4-vj19", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15102", "collection": "thesis", "collection_id": "15102", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02082023-162753604", "primary_object_url": { "basename": "Thesis-YiranYang-final.pdf", "content": "final", "filesize": 31535477, "license": "other", "mime_type": "application/pdf", "url": "/15102/1/Thesis-YiranYang-final.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Laser-Engraved Wearable Sweat Sensor for Metabolic Monitoring", "author": [ { "family_name": "Yang", "given_name": "Yiran (Isabella)", "orcid": "0000-0001-8770-8746", "clpid": "Yang-Yiran-Isabella" } ], "thesis_advisor": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Gharib", "given_name": "Morteza", "orcid": "0000-0003-0754-4193", "clpid": "Gharib-M" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Wearable sensors have shown great potential in health diagnostics and monitoring. Continuous monitoring of metabolites in sweat could potentially offer great insight into a person\u2019s health, but current sweat sensing technology faces challenges in different realms: The sensing strategies are limited and there is a need to achieve high sensitivity for low-concentration targets and widen the detection spectrum of chemical targets. The lack of efficient sweat sampling creates inaccurate sensing results from sweat mixing with skin contaminants or sensing byproducts. Moreover, the lack of evaluation of sweat metabolites with respect to relevant clinical conditions and the lack of scalable fabrication technique pose hurdles in the eventual applications of non-invasive sweat monitoring. In this thesis, efforts advancing progress in these fronts are presented. Chapter 1 establishes a brief topical overview of the sweat-sensing background. In Chapter 2, we demonstrate how to utilize laser-engraving technique to achieve high-performance graphene sensors for electroactive metabolite sensing and vital signs detection. Chapter 3 describes subsequent efforts built on laser-engraved graphene sensors to improve sensing selectivity and widen the detection spectrum to detect non-electroactive targets in sweat. In Chapter 4, design and performance of our laser-engraved microfluidics are described and shown to improve sweat sampling in both exercise-induced and iontophoresis-induced sweating individuals. Chapter 5 presents our endeavors in evaluating sweat biomarkers with clinical conditions in pilot studies involving individuals with gout and metabolic syndrome. In total, the works summarized here expand biology, chemistry, material science, and mechanical engineering, and could potentially facilitate future applications in precision nutrition.", "doi": "10.7907/5yfm-tt16", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:15238", "collection": "thesis", "collection_id": "15238", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312023-034316442", "type": "thesis", "title": "Low-Power and Miniaturized Medical Electronics for In-Vivo Localization and Tracking", "author": [ { "family_name": "Sharma", "given_name": "Saransh", "orcid": "0000-0002-5052-4932", "clpid": "Sharma-Saransh" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Shapiro", "given_name": "Mikhail G.", "orcid": "0000-0002-0291-4215", "clpid": "Shapiro-M-G" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "orcid": "0000-0003-3003-7042", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Traverso", "given_name": "Giovanni", "orcid": "0000-0001-7851-4077", "clpid": "Traverso-Giovanni" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Medical electronic devices are an integral part of the healthcare system today. Significant advances have been made over the past few decades to yield highly miniaturized and low-power medical devices that are suitable for implantable, ingestible, or wearable applications. A key feature of medical devices that is central to their use in many applications is the capability to locate them precisely inside the body, and quite a lot of research effort has been expended in this direction. Location sensing is crucial for several applications: tracking pills in the GI tract, navigation during precision surgeries, endovascular procedures, robotic and minimally invasive surgery, and targeted therapy. The current gold-standard solutions for these procedures include invasive techniques such as endoscopy, or procedures that require repeated use of potentially harmful X-ray radiation such as CT scans. These techniques also require repeated evaluation in a hospital setting and are not conducive for non-clinical environments. While there are several alternative non-ionizing methods for imaging and localization based on electromagnetic tracking, radio-frequency, ultrasound, and optical tracking, none of them are able to simultaneously achieve a high field-of-view of tracking, high spatiotemporal resolution, fully wireless operation and miniaturization of the sensing devices, and system scalability with the number of devices. In this dissertation, we present a radiation-free system for high-precision localization and tracking of miniaturized wireless devices in vivo, using harmless magnetic field gradients.
\r\n\r\nFirst, we demonstrate our system for precision surgery applications. We designed highly miniaturized, wireless and battery-less microdevices, capable of measuring and transmitting their local magnetic field. One such device can be attached to an implant inside the body and another to a surgical tool, such that both can simultaneously measure and communicate the magnetic field at their respective locations to an external receiver. The relative location of the two devices on a real-time display can enable precise surgical navigation without using X-ray fluoroscopy. The prototype device consists of a micro-chip fabricated in 65nm CMOS technology, a 3D magnetic sensor and an inductor-coil. The chip performs wireless power management, wireless bi-directional data-telemetry, and I2C communication with the sensor. Planar electromagnetic coils are designed for creating monotonically varying magnetic fields in the X, Y, and Z directions, resulting in field gradients that encode each spatial point with a unique magnetic field value. The concept of gradient-based spatial encoding is inspired by MRI. The system is tested in vitro to demonstrate a localization accuracy of <100\u00b5m in 3D, the highest reported to the best of our knowledge.
\r\n\r\nSecond, we demonstrate our system for localization and tracking of ingestible microdevices in the GI tract, which is valuable for the diagnosis and treatment of GI disorders. We designed highly miniaturized, low-power, and wireless ingestible devices to sense and transmit their local magnetic field as they travel through the GI tract. These devices consist of a 3D magnetic sensor, a Bluetooth microprocessor and a 2.4GHz Bluetooth antenna for wireless communication, all packaged into a 000-size capsule. The magnetic field sensed by the devices is created by using high-efficiency planar electromagnetic coils that encode each spatial point with a distinct magnetic field magnitude, allowing us to track the location of the devices unambiguously. The system functionality is demonstrated in vivo in large animals under different chronic conditions and disease models to show 3D localization and tracking in real time and in non-clinical settings, with mm-scale spatial resolution, and without using any X-ray radiation. This has the potential for significant clinical benefit for quantitative assessment of GI transit-time, motility disorders, constipation, incontinence, medication adherence monitoring, anatomic targeting for drug delivery, and targeted stimulation therapy.
\r\n\r\nThird, in order to further miniaturize the devices developed for the above two applications and to make them even more low-power, we present a monolithic 3D magnetic sensor in 65nm CMOS technology that measures <5mm\u00b2 in area and consumes 14.8\u00b5W in power while achieving <10\u03bcTrms noise. Our novel 3D magnetic sensor overcomes the challenges faced by traditional magnetic sensors by being fully CMOS compatible and achieving high sensitivity with only \u00b5W-level power, which is in sharp contrast with Hall and Fluxgate sensors. The sensor is comprised of three orthogonal and highly dense metal coils implemented in the 65nm node, which generate a voltage signal in response to AC magnetic fields by electromagnetic induction. The EMF voltage signal is processed by on-chip circuitry that performs low-noise amplification, filtering, peak detection, and 12-bit digitization. Though the sensor can be used for a variety of applications that require AC field sensing, it is particularly useful for biomedical applications\u2014tracking catheters and guidewires during endovascular procedures, minimally invasive surgeries, targeted radiotherapy, and for use as fiducial markers during preoperative planning. The proposed magnetic sensor is demonstrated for use in 3D tracking of catheters using the magnetic-field gradient-based spatial encoding scheme, and achieves 500\u00b5m of mean 3D localization accuracy.
", "doi": "10.7907/xrw0-k789", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:14635", "collection": "thesis", "collection_id": "14635", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05272022-085102678", "primary_object_url": { "basename": "Thesis FINAL - Vincenzo Costanza.pdf", "content": "final", "filesize": 74433912, "license": "other", "mime_type": "application/pdf", "url": "/14635/1/Thesis FINAL - Vincenzo Costanza.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Thermally Responsive Polymers for Wearable Calorimeters", "author": [ { "family_name": "Costanza", "given_name": "Vincenzo", "orcid": "0000-0002-2409-0632", "clpid": "Costanza-Vincenzo" } ], "thesis_advisor": [ { "family_name": "Daraio", "given_name": "Chiara", "orcid": "0000-0001-5296-4440", "clpid": "Daraio-C" } ], "thesis_committee": [ { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Daraio", "given_name": "Chiara", "orcid": "0000-0001-5296-4440", "clpid": "Daraio-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The measurement of the body core temperature (BCT) can provide insightful health information spanning from hypothermia and heat stroke to inflammations and infections. In addition, the continuous monitoring of the BCT can unlock new possibilities for people\u2019s well-being such counting of burnt calories, prediction of the ovulation period in the female population, and for the assessment of mental health issues. However, the integration of a BCT sensor in wearable devices is extremely challenging, since standard methods cannot combine minimal invasiveness with high measurement accuracy. Dual heat flux (DHF) thermometry is a novel technique that allows the precise estimation of BCT from the measurement of skin temperature. Nevertheless, the limited precision of currently available temperature sensors has not favored the wide spread of devices based on this architecture. In this thesis, we present the fabrication of a fully wearable DHF thermometer realized by integrating new polymers with a remarkable temperature sensitivity. In these particular polymers, an increase in temperature results in a change of the ionic conductivity. In the first part of this work, we focus on the understanding of the ion transport mechanism in these polymers and, in particular, on the nature of the interaction between the functional groups present on the polymer backbone and the conducting species (i.e. metal cations and water molecules). We show that the ion\u2019s coordinating environment is the key to make these materials highly sensitive to temperature. The second part of the thesis tackles the fabrication of a BCT sensor, integrating these temperature responsive polymers in an ultrathin DHF thermometer. Building on the understanding of the nature of the temperature response, we optimize the polymer\u2019s composition to obtain a thermal sensitivity that allows a good precision when measuring the BCT. Finally, we characterize the performance of the fabricated DHF thermometer in different conditions, assessing the sensor\u2019s accuracy and response time.", "doi": "10.7907/0hf9-8m62", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14318", "collection": "thesis", "collection_id": "14318", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08042021-231915829", "type": "thesis", "title": "Energy-Efficient Receiver Design for High-Speed Interconnects", "author": [ { "family_name": "Chen", "given_name": "Kuan-Chang", "orcid": "0000-0003-2968-4656", "clpid": "Chen-Kuan-Chang" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Nelson", "given_name": "David", "clpid": "Nelson-David" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "High-speed interconnects are of vital importance to the operation of high-performance computing and communication systems, determining the ultimate bandwidth or data rates at which the information can be exchanged. Optical interconnects and the employment of high-order modulation formats are considered as the solutions to fulfilling the envisioned speed and power efficiency of future interconnects. One common key factor in bringing the success is the availability of energy-efficient receivers with superior sensitivity. To enhance the receiver sensitivity, improvement in the signal-to-noise ratio (SNR) of the front-end circuits, or equalization that mitigates the detrimental inter-symbol interference (ISI) is required. In this dissertation, architectural and circuit-level energy-efficient techniques serving these goals are presented.
\r\n\r\nFirst, an avalanche photodetector (APD)-based optical receiver is described, which utilizes non-return-to-zero (NRZ) modulation and is applicable to burst-mode operation. For the purposes of improving the overall optical link energy efficiency as well as the link bandwidth, this optical receiver is designed to achieve high sensitivity and high reconfiguration speed. The high sensitivity is enabled by optimizing the SNR at the front-end through adjusting the APD responsivity via its reverse bias voltage, along with the incorporation of 2-tap feedforward equalization (FFE) and 2-tap decision feedback equalization (DFE) implemented in current-integrating fashion. The high reconfiguration speed is empowered by the proposed integrating dc and amplitude comparators, which eliminate the RC settling time constraints. The receiver circuits, excluding the APD die, are fabricated in 28-nm CMOS technology. The optical receiver achieves bit-error-rate (BER) better than 1E\u221212 at \u221216-dBm optical modulation amplitude (OMA), 2.24-ns reconfiguration time with 5-dB dynamic range, and 1.37-pJ/b energy efficiency at 25 Gb/s.
\r\n\r\nSecond, a 4-level pulse amplitude modulation (PAM4) wireline receiver is described, which incorporates continuous time linear equalizers (CTLEs) and a 2-tap direct DFE dedicated to the compensation for the first and second post-cursor ISI. The direct DFE in a PAM4 receiver (PAM4-DFE) is made possible by the proposed CMOS track-and-regenerate slicer. This proposed slicer offers rail-to-rail digital feedback signals with significantly improved clock-to-Q delay performance. The reduced slicer delay relaxes the settling time constraint of the summer circuits and allows the stringent DFE timing constraint to be satisfied. With the availability of a direct DFE employing the proposed slicer, inductor-based bandwidth enhancement and loop-unrolling techniques, which can be power/area intensive, are not required. Fabricated in 28-nm CMOS technology, the PAM4 receiver achieves BER better than 1E\u221212 and 1.1-pJ/b energy efficiency at 60 Gb/s, measured over a channel with 8.2-dB loss at Nyquist frequency.
\r\n\r\nThird, digital neural-network-enhanced FFEs (NN-FFEs) for PAM4 analog-to-digital converter (ADC)-based optical interconnects are described. The proposed NN-FFEs employ a custom learnable piecewise linear (PWL) activation function to tackle the nonlinearities with short memory lengths. In contrast to the conventional Volterra equalizers where multipliers are utilized to generate the nonlinear terms, the proposed NN-FFEs leverage the custom PWL activation function for nonlinear operations and reduce the required number of multipliers, thereby improving the area and power efficiencies. Applications in the optical interconnects based on micro-ring modulators (MRMs) are demonstrated with simulation results of 50-Gb/s and 100-Gb/s links adopting PAM4 signaling. The proposed NN-FFEs and the conventional Volterra equalizers are synthesized with the standard-cell libraries in a commercial 28-nm CMOS technology, and their power consumptions and performance are compared. Better than 37% lower power overhead can be achieved by employing the proposed NN-FFEs, in comparison with the Volterra equalizer that leads to similar improvement in the symbol-error-rate (SER) performance.
", "doi": "10.7907/ntem-sn47", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14362", "collection": "thesis", "collection_id": "14362", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09152021-000948244", "primary_object_url": { "basename": "cua_michelle_2022.pdf", "content": "final", "filesize": 30523714, "license": "other", "mime_type": "application/pdf", "url": "/14362/1/cua_michelle_2022.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Exploiting Speckle to Image Deeper in Scattering Media", "author": [ { "family_name": "Cua", "given_name": "Eunice Michelle Chua", "orcid": "0000-0002-0394-757X", "clpid": "Cua-Eunice-Michelle-Chua" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" }, { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical methods for imaging and focusing are advantageous in many scenarios as optics can provide exquisite spatial resolution, has multiple sources of contrast, and does not impart ionizing radiation. However, optical scattering remains a fundamental challenge which limits the depth at which we can perform imaging with good spatial resolution. This challenge motivated our investigations into methods that could make use of the scattered light in order to extend the depth of imaging through or within scattering media. In particular, we focus on answering: (1) Can one 'unscramble' the scattered light in order to recover information about the otherwise hidden object?; and (2) Can we preferentially detect the more forward scattered photons in an efficient manner in order to allow deeper penetration with modest resolution? These two questions are explored in the first two projects of the thesis:
\r\n\r\n1. The development of an imaging system that detects the scattered light and exploits correlations within the scattering process to enable imaging through scattering media at diffraction-limited resolution.
\r\n\r\n2. The introduction of a novel method, termed Speckle-Resolved Optical Coherence Tomography, that sensitively and preferentially detects the more forward scattered photons in a coherent, speckle-resolved fashion to allow deeper imaging at moderate resolution.
\r\n\r\nOptical methods offer the benefit of visualizing samples that would otherwise appear transparent. Using light, one is able to visualize and measure the thickness of transparent films and coatings in a non-contact manner. The third project in my thesis focuses on using light to non-destructively visualize and characterize the evenness of the silicone oil layer that typically coats the inner surface of prefilled syringes. Characterizing the evenness of this silicone oil layer is important as it impacts the functionality of the prefilled syringe and may correlate with particle formation, which is undesirable as the number of particles in a syringe is regulated due to potential health concerns.
", "doi": "10.7907/rcsj-a410", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14454", "collection": "thesis", "collection_id": "14454", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12202021-172349636", "primary_object_url": { "basename": "Zi-Yu_Huang_Thesis.pdf", "content": "final", "filesize": 198300068, "license": "other", "mime_type": "application/pdf", "url": "/14454/1/Zi-Yu_Huang_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Electrical Impedance Spectroscopy-Derived 3D Conductivity Tomography for Atherosclerosis Detection", "author": [ { "family_name": "Huang", "given_name": "Zi-Yu", "orcid": "0000-0001-5998-3097", "clpid": "Huang-Zi-Yu" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Lihong", "orcid": "0000-0001-9783-4383", "clpid": "Wang-Lihong" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Gao", "given_name": "Wei", "orcid": "0000-0002-8503-4562", "clpid": "Gao-Wei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Electrical impedance tomography (EIT) utilizes voltage/current data measured from the surface of interest to reconstruct the electrical conductivity distribution. This results in a noninvasive medical imaging procedure with many applications. Some examples would be: lung ventilation monitoring, breast cancer detection, and fatty liver detection. Non-alcoholic fatty liver disease (NAFLD) is one of the most common causes of cardiometabolic diseases in overweight individuals. The gold standard for NAFLD diagnosis is a liver biopsy which is a risky and invasive procedure. A non-invasive and cost effective method to detect fatty liver is an important unmet clinical need. Due to the distinct electrical properties of fatty tissue versus normal tissue, EIT can be applied to detect the fat infiltrate in the liver. We conducted EIT measurements and reconstructions on 19 subjects where the fat infiltrate was validated by MRI proton-density fat fraction (PDFF). The liver EIT conductivity was shown to be inversely correlated with MRI PDFF, demonstrating the ability of EIT to detect fatty infiltrate in the liver.
\r\n\r\nThis thesis also extends the EIT reconstruction to detect atherosclerosis, which is a build-up of fatty tissue in the arteries (plaque). Some plaques are prone to rupture and the current gold standard has a false negative rate of 20 % when distinguishing between vulnerable plaque and stable plaque. We sought to use EIT to detect the fatty content (mainly oxidize LDL) inside these vulnerable plaques. Therefore, the reconstruction method was modified into an outward setting that can measure from the inner surface of interest. Ex vivo experiments have demonstrated the ability to detect the location of fatty tissue in swine aorta. This technique has the potential to detect vulnerable plaque. However, the dimension of the device and the required electrode number limits the application from in vivo animal artery experiments.
\r\n\r\nFinally EIS-derived EIT, a new method we proposed, utilizes impedance values at a fixed frequency to solve for the conductivity distribution. This approach circumvents the mathematically ill-posed problem found when performing traditional EIT methods. We designed a 6-point EIS electrode array that was circumferentially configured to a balloon catheter and deployed in Yorkshire mini-pigs with induced stenosis in the right carotid artery. The EIS spectra demonstrated an elevated impedance in the right carotid arteries and the EIS-derived EIT mappings were reconstructed. The low conductivity regions in the EIS-derived EIT mappings were correlated with the positive E06 immunostaining for oxLDL-laden regions. Thus, we establish the capability of 3D EIS-derived EIT to detect oxLDL-laden arterial walls with translational implication to predict metabolically active plaques prone to acute coronary syndromes.
", "doi": "10.7907/n0md-h379", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:14536", "collection": "thesis", "collection_id": "14536", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03312022-192034489", "primary_object_url": { "basename": "D_Elliott_Williams_Doctoral_Thesis_Shape_Changing_Phased_Arrays.pdf", "content": "final", "filesize": 107493311, "license": "other", "mime_type": "application/pdf", "url": "/14536/15/D_Elliott_Williams_Doctoral_Thesis_Shape_Changing_Phased_Arrays.pdf", "version": "v12.0.0" }, "type": "thesis", "title": "Shape-Changing Phased Arrays", "author": [ { "family_name": "Williams", "given_name": "David Elliott", "orcid": "0000-0002-6213-4712", "clpid": "Williams-David-Elliott" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Bhattacharya", "given_name": "Kaushik", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Historically, increasing the degrees of freedom in electromagnetic structures has revolutionized the capabilities of wireless systems and introduced new applications. While research on phased arrays has explored everything from antenna drive settings to the element placement, the array geometry is assumed to be a fixed parameter. This thesis summarizes the author's work developing shape-changing phased arrays. It demonstrates the fundamental trade-off between gain and steering range for a given geometry. Measurements of the first shape-changing phased array both verify this theory and demonstrate the ability to break this trade-off using geometric reconfiguration. In addition, the mathematical consequences of shape-change and their impact on the arrays electromagnetic properties are discussed. Programmable passive switching networks on flexible sheets embedded in the array are proposed to address these challenges. The ability of these structures to enhance array performance is demonstrated by in-situ optimization experiments on a demonstration array. The associated optimization problem is characterized with a statistical analysis on a simulated array. Finally, avenues for further research are proposed.
", "doi": "10.7907/r6f1-zq65", "publication_date": "2022", "thesis_type": "phd", "thesis_year": "2022" }, { "id": "thesis:13957", "collection": "thesis", "collection_id": "13957", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09182020-074010855", "type": "thesis", "title": "Active Flat Optics Wavefront Manipulation for Imaging, Ranging, and Sensing", "author": [ { "family_name": "Fatemi", "given_name": "Seyed Mohammadreza", "orcid": "0000-0001-9081-2608", "clpid": "Fatemi-Seyed-Mohammadreza" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Faraon", "given_name": "Andrei", "orcid": "0000-0002-8141-391X", "clpid": "Faraon-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The emergence and maturity of integrated photonic platforms over the past decade allowed for reliable integration of a large number of photonic components on a single substrate. This ability to process and control coherent light on a chip is a potential pathway for the realization of novel low-cost systems capable of non-conventional functionalities for optical wavefront engineering. In this thesis, integrated active flat optics architectures for generation, manipulation, and reception of optical wavefronts are investigated. In particular, the application of such systems for imaging, ranging, and sensing are studied and multiple photonic systems including a large scale transmitter, a high-sensitivity receiver, and a high-resolution transceiver are demonstrated.
\r\n\r\nFor generation of optical wavefronts, solutions for engineering a radiative optical waveform via emission by an array of nano-photonic antennas are studied and a chip-scale photonic transmitter is implemented. The transmitter forms an optical phased array with a novel architecture in a CMOS compatible silicon photonics process which not only dispenses with the limitations of previously demonstrated systems but also yields a narrower beamwidth leading to a higher resolution. Moreover, an integrated adaptive flat optical receiver architecture that collects samples of the incident light and processes it on-chip with high detection sensitivity is implemented. To detect the optical samples with a high signal to noise ratio, an optoelectronic mixer is proposed and designed that down-converts the optical signals received by each antenna to a radio frequency signal in the electronic domain, provides conversion gain, and rejects interferers. This system allows arbitrary wavefront manipulation of the received signal by adapting itself to new conditions \u2014 a capability that does not exist in conventional cameras. Using this system, we realized the first high-sensitivity optical phased array receivers with one-dimensional and two-dimensional apertures and the functionality of the chips as ultra-thin lens-less cameras were demonstrated. To achieve a high-resolution integrated photonic 3D imager with low system complexity, a double spectral sampling method is developed through a special wavefront sampling arrangement on the transmitter and receiver apertures. This transceiver architecture includes a multi-beam transmitter and a high-sensitivity receiver that can distinguish the illuminated points separately and process them simultaneously using a digital signal processor.
\r\n\r\nMoreover, novel ultra-low power architectures for generation and reception of short RF/microwave pulses are explored. Such systems have a broad range of applications including imaging and ranging. In this study, the capability of generating and receiving orthogonal Hermite pulses of various orders using a capacitor-only time-varying network is demonstrated.
", "doi": "10.7907/7e5p-9r23", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:13857", "collection": "thesis", "collection_id": "13857", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08172020-115024354", "type": "thesis", "title": "Precision at Scale: System Design from Tiny Biosensors to Giant Arrays", "author": [ { "family_name": "Gal-Katziri", "given_name": "Matan", "orcid": "0000-0001-9100-1188", "clpid": "Gal-Katziri-Matan" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Marandi", "given_name": "Alireza", "orcid": "0000-0002-0470-0050", "clpid": "Marandi-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In order to change the world, technological advancements must be made affordable and available for the general public to use. In other words, we must be able to scale our inventions effectively. Silicon integrated circuits are crucial components in scaling electronic systems because they are mass producible and offer a phenomenal cost-to-complexity ratio. This thesis summarizes the author\u2019s work on highly scalable sensor and array systems. It presents three high precision systems, that demonstrate how the use of highly functional radio-frequency integrated circuits enables the realization of previously unfeasible architectures.", "doi": "10.7907/t3cz-c785", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:14080", "collection": "thesis", "collection_id": "14080", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:02162021-124026838", "primary_object_url": { "basename": "Aroutin_Khachaturian Thesis Final.pdf", "content": "final", "filesize": 42602622, "license": "other", "mime_type": "application/pdf", "url": "/14080/1/Aroutin_Khachaturian Thesis Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Large-Scale Photonics Integration: Data Communications to Optical Beamforming", "author": [ { "family_name": "Khachaturian", "given_name": "Aroutin", "orcid": "0000-0001-8304-3302", "clpid": "Khachaturian-Aroutin" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "orcid": "0000-0003-1783-1380", "clpid": "Vahala-K-J" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated photonics is an emerging technology that has begun to transform our way of life with the same amount of impact that integrated CMOS electronics has. Currently, photonics integration is orders of magnitude less complicated than its electronics counterparts. Nonetheless, it serves as one of the main driving forces to meet the exponentially increasing demand for high-speed and low-cost data transfer in the Information Age. It also promises to provide solutions for next-generation high-sensitivity image sensors and precision metrology and spectroscopy instruments. In this thesis, integrated photonics architectures for solid-state photonic beamforming and processing are investigated for high-resolution and high sensitivity lens-free transceiver applications. Furthermore, high-efficiency integrated electro-optical modulators aiming to meet the demand of high-density photonic integration with improved modulation efficiency, small footprint, and lower insertion loss are investigated.
\r\n\r\nTwo integrated photonic solid-state beamforming architectures incorporating two-dimensional apertures are explored. First, a novel transceiver architecture for remote sensing, coherent imaging, and ranging applications is demonstrated. It reduces system implementation complexity and offers a methodology for very-large-scale coherent transceiver beamforming applications. Next, a transmitter beamforming architecture inspired by the diffraction pattern of the slit annular ring is analyzed and demonstrated. This transceiver architecture can be used for coherent beamforming applications such as imaging and point-to-point optical communication. Finally, a coherent imager architecture for high-sensitivity three-dimensional imaging and remote-sensing applications is present. This novel architecture can suppress undesired phase fluctuations of the optical carrier signal in the illumination and reference paths, providing higher resolution and higher acquisition speed than previous implementations.
\r\n\r\nMoreover, several compact, high-speed CMOS compatible modulators that enable high-density photonic integration are explored. Ultra-compact and low insertion loss silicon-organic-hybrid modulators are designed and implemented for high-speed beamforming and high-efficiency complex signal modulation applications. Finally, a novel integrated nested-ring assisted modulator topology is analyzed and implemented for high-density and high modulation efficiency applications.
", "doi": "10.7907/xjby-xn13", "publication_date": "2021", "thesis_type": "phd", "thesis_year": "2021" }, { "id": "thesis:11136", "collection": "thesis", "collection_id": "11136", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07262018-030251324", "type": "thesis", "title": "Periodically Disturbed Oscillators", "author": [ { "family_name": "Hong", "given_name": "Brian Daffern", "orcid": "0000-0001-8099-0312", "clpid": "Hong-Brian-Daffern" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "By controlling the timing of events and enabling the transmission of data over long distances, oscillators can be considered to generate the \"heartbeat\" of modern electronic systems. Their utility, however, is boosted significantly by their peculiar ability to synchronize to external signals that are themselves periodic in time. Although this fascinating phenomenon has been studied by scientists since the 1600s, models for describing this behavior have seen a disconnect between the rigorous, methodical approaches taken by mathematicians and the design-oriented, physically-based analyses carried out by engineers. While the analytical power of the former is often concealed by an inundation of abstract mathematical machinery, the accuracy and generality of the latter are constrained by the empirical nature of the ensuing derivations. We hope to bridge that gap here.
\r\n\r\nIn this thesis, a general theory of electrical oscillators under the influence of a periodic injection is developed from first principles. Our approach leads to a fundamental yet intuitive understanding of the process by which oscillators lock to a periodic injection, as well as what happens when synchronization fails and the oscillator is instead injection pulled. By considering the autonomous and periodically time-varying nature that underlies all oscillators, we build a time-synchronous model that is valid for oscillators of any topology and periodic disturbances of any shape. A single first-order differential equation is shown to be capable of making accurate, quantitative predictions about a wide array of properties of periodically disturbed oscillators: the range of injection frequencies for which synchronization occurs, the phase difference between the injection and the oscillator under lock, stable vs. unstable modes of locking, the pull-in process toward lock, the dynamics of injection pulling, as well as phase noise in both free-running and injection-locked oscillators. The framework also naturally accommodates superharmonic injection-locked frequency division, subharmonic injection-locked frequency multiplication, and the general case of an arbitrary rational relationship between the injection and oscillation frequencies. A number of novel insights for improving the performance of systems that utilize injection locking are also elucidated. In particular, we explore how both the injection waveform and the oscillator's design can be modified to optimize the lock range. The resultant design techniques are employed in the implementation of a dual-moduli prescaler for frequency synthesis applications which features low power consumption, a wide operating range, and a small chip area.
\r\n\r\nFor the commonly used inductor-capacitor (LC) oscillator, we make a simple modification to our framework that takes the oscillation amplitude into account, greatly enhancing the model's accuracy for large injections. The augmented theory uniquely captures the asymmetry of the lock range as well as the distinct characteristics exhibited by different types of LC oscillators. Existing injection locking and pulling theories in the available literature are subsumed as special cases of our model. It is important to note that even though the veracity of our theoretical predictions degrades as the size of the injection grows due to our framework's linearization with respect to the disturbance, our model's validity across a broad range of practical injection strengths are borne out by simulations and measurements on a diverse collection of integrated LC, ring, and relaxation oscillators. Lastly, we also present a phasor-based analysis of LC and ring oscillators which yields a novel perspective into how the injection current interacts with the oscillator's core nonlinearity to facilitate injection locking.
", "doi": "10.7907/W0A7-4258", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11553", "collection": "thesis", "collection_id": "11553", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282019-120721714", "primary_object_url": { "basename": "Microresonator_Brillouin_Laser_Gyroscope.pdf", "content": "final", "filesize": 21222162, "license": "other", "mime_type": "application/pdf", "url": "/11553/33/Microresonator_Brillouin_Laser_Gyroscope.pdf", "version": "v13.0.0" }, "type": "thesis", "title": "Microresonator Brillouin Laser Gyroscope", "author": [ { "family_name": "Lai", "given_name": "Yu-Hung", "orcid": "0000-0002-9639-6569", "clpid": "Lai-Yu-Hung" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical Gyroscopes are among the most accurate rotation-measuring devices and are widely used for navigation and accurate compasses. With the advent of integrated photonics for complex telecommunication chips, there has been interest in the possibility of chip-scale optical gyroscopes. Besides the potential benefits of miniaturization, such solid-state systems would be robust and resistant to shock. In this thesis, we investigate a chip-based optical gyroscope using counter-propagating Brillouin lasers on a monolithic silicon chip. The near-degenerate lasers mimic a commercial ring laser gyroscope including the existence of a locking band. By using physical properties associated with the Brillouin process, a solid-state unlocking method is demonstrated. We focus on three topics to explore the potential of the counter-propagating Brillouin-laser gyroscope. First, we explore the physics of the counter-propagating Brillouin lasers by deriving the theory to link the passive cavity mode with the lasing gain medium. We explicitly show how the dispersion, Kerr nonlinearity, dissipative coupling, and Sagnac sensing affect the beating frequency of the Brillouin lasers. Second, we experimentally demonstrate the performance of the gyroscope. Most notably, the gyroscope is used to measure the rotation of the Earth, representing an important milestone for chip-scale optical gyroscopes. Third, we investigate the non-Hermitian interaction between the counter-propagating Brillouin lasers. We test the recent prediction of the EP-enhanced Sagnac effect, and observe a Sagnac scale factor boost by over 4X by measurement of rotations applied to the resonator. Our research shows the feasibility of the chip-based Brillouin laser gyroscope. This gyroscope paves the way towards an all-optical inertial guidance system.
", "doi": "10.7907/10XE-G776", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11569", "collection": "thesis", "collection_id": "11569", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302019-123348477", "primary_object_url": { "basename": "Shapero_Aubrey_2019_thesis_one_sided.pdf", "content": "final", "filesize": 83602799, "license": "other", "mime_type": "application/pdf", "url": "/11569/1/Shapero_Aubrey_2019_thesis_one_sided.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Long Term Implantable Pressure Sensors", "author": [ { "family_name": "Shapero", "given_name": "Aubrey Michael", "orcid": "0000-0002-8036-3623", "clpid": "Shapero-Aubrey-Michael" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Humayun", "given_name": "Mark", "clpid": "Humayun-M" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The benefits of implantable pressure sensors for continuous monitoring of diseases like glaucoma or hydrocephalus has been well established, but it has been difficult to achieve accurate pressure sensing in the body for more than one month. In this thesis, a general MEMS pressure sensor packaging method called parylene-oil-encapsulation is developed and analyzed in order to make commercial barometers for use in air suitable for implantation inside the body long term. Accelerated aging bench top data is presented and a wireless implantable intraocular pressure sensor has been built towards proving the viability of the packaging method in vivo.
", "doi": "10.7907/SX5J-VM54", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11508", "collection": "thesis", "collection_id": "11508", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05112019-120905666", "primary_object_url": { "basename": "Mahsa_thesis_5_8_2019.pdf", "content": "final", "filesize": 142818215, "license": "other", "mime_type": "application/pdf", "url": "/11508/2/Mahsa_thesis_5_8_2019.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Dielectric Metasurfaces from Fundamentals to Applications", "author": [ { "family_name": "Kamali", "given_name": "Seyedeh Mahsa", "orcid": "0000-0002-6968-811X", "clpid": "Kamali-Seyedeh-Mahsa" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Wang", "given_name": "Lihong", "clpid": "Wang-Lihong" }, { "family_name": "Minnich", "given_name": "Austin J.", "clpid": "Minnich-A-J" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "In the past few decades, the advancements in nanotechnology have significantly altered many fields of science and technology, especially electronics and integrated photonics. Free-space optics, on the other hand, has remained mostly unaffected, and even today \"optics\" reminds us of carefully shaped and polished pieces of various types of glasses and crystals lumped into lenses and beam shapers. Several of these devices are then combined into more complicated optical systems like microscopes and pulse shapers that are expensive, bulky, sensitive to various environmental factors, and require several alignment steps. This thesis contains my work on designing and utilizing structures engineered at the nano-scale, which are called metasurfaces, to implement compact optical elements and systems with capabilities beyond those of conventional refractive and diffractive optics. My contributions to this field are two-fold: I have developed and contributed to the development of new concepts that take metasurfaces beyond conventional difractive optics in various aspects, in addition to paradigm changing platforms for optical element and system design. Here, I first give an overview and a brief history about optical metasurfaces. Next I discuss the unprecedented capabilities of metasurfaces in controlling light based on its degrees of freedom like illumination angle and polarization. Then, I will focus on various novel metasurface platforms of conformal and tunable metasurfaces, 3D metasurface beam shapers, and integrated metasurfaces. I conclude with an outlook on future potentials and challenges that need to be overcome for realizing their wide-spread applications.", "doi": "10.7907/TPN1-XA53", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11733", "collection": "thesis", "collection_id": "11733", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06102019-031412552", "primary_object_url": { "basename": "Dvin_Adalian_Thesis_2019_Caltech_FinalDraft_June9_V6.pdf", "content": "final", "filesize": 4568651, "license": "other", "mime_type": "application/pdf", "url": "/11733/1/Dvin_Adalian_Thesis_2019_Caltech_FinalDraft_June9_V6.pdf", "version": "v11.0.0" }, "type": "thesis", "title": "Development and Dynamics of Microfabricated Enzymatic Biosensors", "author": [ { "family_name": "Adalian", "given_name": "Dvin Artashes-Boghos", "clpid": "Adalian-Dvin-Artashes-Boghos" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Daraio", "given_name": "Chiara", "orcid": "0000-0001-5296-4440", "clpid": "Daraio-C" }, { "family_name": "Phillips", "given_name": "Robert B.", "orcid": "0000-0003-3082-2809", "clpid": "Phillips-R" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Scherer", "given_name": "Axel", "orcid": "0000-0002-2160-9064", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "We have extended the application of microfabrication techniques to all parts of electrochemical enzymatic sensor processing and characterized the behavior of the resulting new sensor geometries. Improved and parallelized enzyme immobilization techniques utilizing spin coating along with porous sputtered platinum barrier layers are implemented on microfabricated platinum electrodes on silicon wafer substrates as well as on millimeter-scale wireless CMOS potentiostats. Functional biosensor sensitivities and linear ranges were observed with multi-month lifetimes, demonstrating that the enzyme layer fabrication process is compatible with precise and massively parallelized CMOS fabrication, making further progress toward the production of low cost and low-tissue impact fully implantable miniaturized biosensors.", "doi": "10.7907/7GHS-NX49", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11548", "collection": "thesis", "collection_id": "11548", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282019-074707723", "primary_object_url": { "basename": "Full_Thesis_Final.pdf", "content": "final", "filesize": 13376941, "license": "other", "mime_type": "application/pdf", "url": "/11548/1/Full_Thesis_Final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Oxygen Transporter and Generator Devices to Treat Diabetic Retinopathy", "author": [ { "family_name": "Scianmarello", "given_name": "Nicholas E.", "orcid": "0000-0002-1207-4029", "clpid": "Scianmarello-Nicholas-E" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Humayun", "given_name": "Mark", "clpid": "Humayun-M" }, { "family_name": "Gao", "given_name": "Wei", "clpid": "Gao-Wei" }, { "family_name": "Wang", "given_name": "Lihong", "clpid": "Wang-Lihong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In recent years, Micro-Electrical Mechanical Systems (MEMS) have opened new areas of the human body to non-pharmacological treatment. Miniaturized implants have started to appear in volume or power constrained areas, such as the eye and the heart. In particular, the eye benefits from miniaturization, as it is very sensitive to pressure and volumetric changes, which can affect eyesight and blood flow.
\r\n\r\nDiabetic retinopathy is the worldwide leading cause of blindness among working age adults. As the numbers of diabetics increases, so does the number of retinopathies. By 2030, 191 million people are expected to be affected by the disease. As a patient\u2019s retinopathy progresses, the chronic hyperglycemia from diabetes causes permanent changes to the vasculature; vessels become leaky and occluded, tissue becomes hypoxic due to this ischemia and begins to release vascular endothelial growth factor (VEGF) to promote angiogenesis.
\r\n\r\nCurrently, treatments exist only for severe non-proliferative or proliferative DR, and rely on blocking VEGF (vascular endothelial growth factor) or panretinal laser photocoagulation to reduce retinal metabolic demand. VEGF antagonists are expensive; costing up to $164k per quality life adjusted year and must be administered by intravitreal injections monthly. Laser photocoagulation also requires retreatment and is known to reduce peripheral vision\u2014up to 20% of the peripheral retina is ablated. Another treatment approach may be to supply oxygen. Oxygen is a strong vasoconstrictor and suppresses the hypoxic signaling that leads to release of VEGF. These two effects reduce the plasma volume leaked into tissue, which in turn reduces edema, and may help prevent ischemic related cell death. Literature supports this assertion. A study of nasally inspired oxygen in patients with macular edema showed a reduction of edema and improvement of visual acuity following 3 months of treatment. Another study on rabbits with an induced ischemia demonstrated that intravitreal oxygenation maintained the retina to a near healthy condition.
\r\n\r\nIn this thesis, two devices, the oxytransporter and oxygenerator, that treat diabetic retinopathy are designed and tested. The former shuttles oxygen from areas of high concentration to the ischemic retina. The latter generates oxygen by electrolysis.
\r\n\r\nThis thesis is grounded on a computational model of oxygen consumption in the retina. To estimate the oxygen consumption, the model accounts for the anatomical distribution of tissue and vasculature in the retina. Previous models in literature averaged over the effects in the inner retina. The model estimates that the devices must supply 0.25nmol/s of oxygen to the human macula with an oxygen tension dependent on the degree of ischemia.
\r\n\r\nA nanoporous filler material was developed and integrated into the oxytransporter to allow this device to operate in the high humidity environment of the eye. The material is capable of withstanding an environment with water vapor 1.4 times the bulk saturation pressure. Theory behind the material was tested and compared to simulation. Benchtop testing over a month demonstrated the stability of the device in conditions similar to the eye. This oxytransporter was implanted in rabbits and the diffusor, or output membrane, reached the favorable mark of 100mmHg in the vitreous humor from atmospheric oxygen alone. This is estimated to be sufficient to treat a mild to moderate ischemia in humans.
\r\n\r\nThe oxygenerator is powered from a coil up to 3cm away, and can provide 0.25nmol/s continuously with an oxygen tension of up to 300mmHg for a human sized diffusor. A steady state test demonstrated the capability of maintaining the oxygen tension in the device by modulating the input power. The device is replenished through osmosis from the vitreous humor, and can absorb moisture at a rate comparable to the required oxygen consumption. One week implantation in vivo in rabbits demonstrated that the oxygen tension exceeded 200mmHg at the diffusor, which is estimated to be sufficient to treat severe ischemia.\r\nFuture work should involve a study of the long term effects of oxygen in an ischemic animal model.
", "doi": "10.7907/JCS2-8E12", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:11551", "collection": "thesis", "collection_id": "11551", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282019-104728085", "primary_object_url": { "basename": "Brake_Thesis_2019.pdf", "content": "final", "filesize": 36468307, "license": "other", "mime_type": "application/pdf", "url": "/11551/1/Brake_Thesis_2019.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Seeing Through the Fog: Using Scattered Light to Peer Deeper into Biological Tissue\r ", "author": [ { "family_name": "Brake", "given_name": "Joshua Harris", "orcid": "0000-0002-5113-6886", "clpid": "Brake-Joshua-Harris" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Lihong", "clpid": "Wang-Lihong" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Gradinaru", "given_name": "Viviana", "clpid": "Gradinaru-V" }, { "family_name": "Chung", "given_name": "Euiheon", "clpid": "Chung-Euiheon" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Optical scattering is a fundamental problem in biomedical optics and limits most optical techniques to shallow operating depths less than 1 millimeter. However, although the scattering behavior of tissue scrambles the information it contains, it does not destroy it. Therefore, if you can unscramble the scattered light, it increases the accessible imaging depths up the absorption limit of light (several centimeters deep).
\r\n\r\nOne such way to beat optical scattering is using wavefront shaping. Borrowing ideas from adaptive optics in astronomy and phased arrays in radar and ultrasonic imaging, the basic concept of wavefront shaping is to control the phase and amplitude of the light field in order to harness scattered light. Using wavefront shaping techniques, scattered light can be used to form focal spots or transmit information through or inside optically scattering media. Furthermore, even without correcting for scattering directly by shaping the input light field, the properties of the scattered light can be analyzed to recover information about the structure and dynamic properties of a sample using methods from diffuse optics.
\r\n\r\nThe main contributions of this thesis are along these two lines of research: moving wavefront shaping toward more practical applications and developing new techniques to recover useful physiological information from scattered light. This is developed through three main projects: (1) an investigation of how dynamic samples impact the scattering process and the practical implications of these dynamics on wavefront shaping systems, (2) the development of a wavefront shaping system combining light and ultrasound to focus light inside acute brain slices to improve light delivery for optogenetics, (3) a novel method to sensitively detect the dynamics of scattered light and use it to tease out information about the flow of blood within the tissue sample of interest.
", "doi": "10.7907/0PP8-2E39", "publication_date": "2019", "thesis_type": "phd", "thesis_year": "2019" }, { "id": "thesis:10607", "collection": "thesis", "collection_id": "10607", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12132017-132404589", "type": "thesis", "title": "Nanoscale Field Emission Devices", "author": [ { "family_name": "Jones", "given_name": "William Maxwell", "orcid": "0000-0002-8610-2176", "clpid": "Jones-William-Maxwell" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "DeRose", "given_name": "Guy A.", "clpid": "DeRose-Guy-A" }, { "family_name": "Neches", "given_name": "Philip M.", "clpid": "Neches-Philip-M" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "This thesis outlines work done to produce in-plane nanoscale field emission devices. Field emission, the process of quantum tunneling electrons from a conductor into a vacuum, has been theorized as a device concept for almost as long as integrated circuits have existed. This is because the micro- and nanoscale dimensions of integrated circuits make field emission possible at modest voltages, and because the physics of field emission and conduction in a vacuum channel suggest that field emission devices can operate at extremely high frequencies and in harsh environments where CMOS devices face challenges. Yet despite many attempts to make practical field emission devices none have risen to the level of commercial products. These attempts were stymied by short lifetimes, high operating voltages, and the necessity for vacuum enclosure. In this thesis work, I outline how new fabrication technologies like high resolution electron beam lithography, atomic layer deposition, and refinement in reactive ion etching make lateral field emission devices with extremely short vacuum channels practical. The demonstrated devices can operate at near CMOS voltages and at atmospheric pressures, and are robust to emitting tip destruction. These devices are prime candidates for integration into demonstration circuits.
\r\n\r\nThe second part of this thesis outlines work done in an emerging field to combine field emission with plasmonics for practical devices. The tunneling process in field emission depends exponentially on the magnitude of the instantaneous electric field, either static or time-varying, at the emitting surface. While it has long been known that using extremely powerful pulsed lasers one can field emit electrons from a metallic surface, the combination of plasmonics into a field emitting device has the potential to dramatically lower the incident optical power needed to produce field emission. This could enable extremely fast opto-electronic devices. This thesis presents work in progress to realize a plasmonically enhanced field emission opto-electronic modulator that is designed to operate at 1550 nm and is integratable with existing silicon photonics platforms.
", "doi": "10.7907/Z94B2ZHZ", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10483", "collection": "thesis", "collection_id": "10483", "cite_using_url": "https://resolver.caltech.edu/CaltechThesis:10042017-102201104", "type": "thesis", "title": "Integrated Ultra-High-Q Nonlinear Photonic Platform for On-Chip Optoelectronic Systems", "author": [ { "family_name": "Yang", "given_name": "Kiyoul", "orcid": "0000-0002-0587-3201", "clpid": "Yang-Kiyoul" } ], "thesis_advisor": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" } ], "thesis_committee": [ { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Atwater", "given_name": "Harry Albert", "clpid": "Atwater-H-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "local_group": [ { "literal": "Institute for Quantum Information and Matter" }, { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "Silicon technology provided a concrete basis of the integrated microelectronics revolution, and it might usher disruptive advances in photonics again. An integrated photonic system can potentially revolutionize instrumentation, time standards, spectroscopy, and navigation. Driven by these applications, various high-Q platforms have emerged over the last decade. However, applications require to satisfy challenging combinations of ultra-high-Q (UHQ) cavity performance, monolithic integration, and nonlinear cavity designs: the monolithic integration of UHQ devices still remains elusive. In this thesis, an integrated UHQ microcavity is demonstrated for the first time. A silicon nitride waveguide is monolithically integrated with a silicon oxide cavity, and the integrated waveguide can provide nearly universal interface to other photonic devices. Significantly, this thesis discusses far beyond setting a new record for integrated Q factor: the integrated UHQ cavity provides functionality as soliton source with electronic-repetition-rates. Demonstration of low-pump-power soliton generation at 15 GHz was previously possible in only discrete devices but essentially required for integrated self-referenced comb, which can unlock new level of performance and scale in an optoelectronic system. In addition, nonlinear cavity design is another outstanding challenge towards a further development on the optoelectronic system, and will be discussed in this thesis. The dispersion-engineered platform can potentially tailor the spectral bandwidth of frequency comb, and extend the frequency comb to visible and ultraviolet band. Importantly, the design methods are directly transferable to the integrated platform.", "doi": "10.7907/Z96T0JTQ", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10442", "collection": "thesis", "collection_id": "10442", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:09202017-124555409", "primary_object_url": { "basename": "Horie_Yu_2018.pdf", "content": "final", "filesize": 59827475, "license": "other", "mime_type": "application/pdf", "url": "/10442/1/Horie_Yu_2018.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Controlling the Flow of Light Using High-Contrast Metastructures", "author": [ { "family_name": "Horie", "given_name": "Yu", "orcid": "0000-0001-7083-1270", "clpid": "Horie-Yu" } ], "thesis_advisor": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "thesis_committee": [ { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "A new class of planar optical components and devices has emerged using subwavelength metastructures with a strong contrast in refractive indices. High-contrast metastructures have shown promises to manipulate optical fields in an extraordinary way and to replace conventional bulky optical elements by their low-profile analogs, typically with subwavelength-scale features. We elucidate the underlying principle, how these seemingly low-profile geometries render unique optical responses, using the coupled-mode analysis in a multimode waveguide. Moreover, strong field localization in high-index structures allows us to interpret each single element in the metastructures as a low-quality-factor resonator (or a localized scatterer), permitting us to realize designer surface that shapes phase, amplitude, and polarization of light in free space, also known as an optical metasurface. The remainder of the thesis is devoted to explore novel applications in optics using high-contrast metastructures. One of the particularly interesting applications is to use them in an optical resonator. Specifically, we demonstrate to incorporate high-contrast subwavelength grating reflectors and dielectric metasufaces in a vertical Fabry\u2013Perot cavity, and show that we can flexibly tune the resonance frequency by the subwavelength patterning. With this technique, we envision the realization of compact, on-chip spectrometers when integrating them on a photodetector array. Secondly, we investigate the use of high-contrast subwavelength gratings in visible wavelengths. We perform the optimization of their geometries and demonstrate a set of RGB color filters, down to near a micrometer in the pixel size. This platform exhibits unique performances such as high efficiency, angular insensitivity, and color tunability by the design. A novel device concept is also explored, where a high-contrast subwavelength grating reflector is integrated on a silicon platform to constitute an active resonant antenna, enabling high-speed, phase-dominant modulation by means of thermo-optic effect of silicon. We demonstrate an array of such active antennas, yielding a beam deflection capability. This justifies the robustness of our device design, enabling a large-scale integration of high-speed, phase-dominant spatial light modulators. Finally, we introduce a disorder-engineered metasurface in the context of wavefront shaping. Recently, wavefront shaping with disordered media has demonstrated optical manipulation capabilities beyond those of conventional optics, but translating this class of technology into a practical use has remained challenging due to enormous amounts of information needed to be characterized as the input-output responses. As a paradigm shift, we propose the use of disorder-engineered metasurface in wavefront shaping, where the disorder is programmatically designed and makes the system characterization-free prior to use. With this approach, we demonstrate high numerical aperture focusing in an extended volume as well as wide-field fluorescence imaging with unprecedented performances.
", "doi": "10.7907/Z94X5604", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:11022", "collection": "thesis", "collection_id": "11022", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042018-194533722", "primary_object_url": { "basename": "phd-thesis_June2018.pdf", "content": "final", "filesize": 71599010, "license": "cc_by_nc", "mime_type": "application/pdf", "url": "/11022/1/phd-thesis_June2018.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Silicon Integrated Arrays: From Microwave to IR", "author": [ { "family_name": "Abiri", "given_name": "Behrooz", "orcid": "0000-0002-3317-2752", "clpid": "Abiri-Behrooz" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated chips have enabled realization and mass production of complex systems in a small form factor. Through process miniaturization many novel applications in silicon photonics and electronic systems have been enabled. In this thesis I have provided several examples of innovations that are only enabled by integration. I have also demonstrated how electronics and photonics circuits can complement each other to achieve a system with superior performance.
", "doi": "10.7907/MNYK-Y158", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10538", "collection": "thesis", "collection_id": "10538", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10242017-104926655", "type": "thesis", "title": "The Coherence Collapse Regime of High-Coherence Si/III-V Lasers and the Use of Swept Frequency Semiconductor Lasers for Full Field 3D Imaging", "author": [ { "family_name": "Harfouche", "given_name": "Mark", "orcid": "0000-0002-4657-4603", "clpid": "Harfouche-Mark" } ], "thesis_advisor": [ { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" } ], "thesis_committee": [ { "family_name": "Painter", "given_name": "Oskar J.", "clpid": "Painter-O" }, { "family_name": "Yariv", "given_name": "Amnon", "clpid": "Yariv-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Faraon", "given_name": "Andrei", "clpid": "Faraon-A" } ], "local_group": [ { "literal": "Kavli Nanoscience Institute" }, { "literal": "div_eng" } ], "abstract": "The semiconductor laser is the linchpin of optical communication and is now also penetrating a wide spectrum of new applications such as biomedical sensing, coherent communication, metrology, and time keeping. These require a higher degree of temporal coherence than is available from the present generation. Recently, it has been proposed and shown that heterogeneously integrated lasers on silicon and InGaAsP can be used to design high coherence single mode lasers with a much narrower linewidth than their all InGaAsP counterparts. Unfortunately, these lasers suffer from large thermal impedances and their optical feedback characteristics have not yet been explored. In the first part of this thesis, we will explore how flip chip bonding can help decrease the thermal impedance of these lasers to improve their overall performance and show that these lasers can provide up to 20 dB of optical isolation compared to their all III-V counterparts.
\r\n\r\nIn the second part of this thesis, we will report on the use of commercially available semiconductor lasers, in conjunction with an optical modulator to obtain high-resolution tomographic images in one shot without any moving parts. The electronic control over the imaged depth of this novel tomographic imaging camera enables it to monitor arbitrary depth slices in rapid succession over a depth range limited only by the coherence length of the laser. Not only does this imaging modality acquire the transverse image intensity (x,y) distribution of the light reflected from a particular depth, but also the phase of the reflected light enabling imaging beyond the conventional depth of field of the lens. This has important implications in applications requiring high lateral resolution images where the shallow depth of field would often require mechanical scanning of the lens elements to change the imaged depth.
", "doi": "10.7907/Z9W66J07", "publication_date": "2018", "thesis_type": "phd", "thesis_year": "2018" }, { "id": "thesis:10232", "collection": "thesis", "collection_id": "10232", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05312017-143935777", "primary_object_url": { "basename": "thesis_v1.pdf", "content": "final", "filesize": 191384516, "license": "other", "mime_type": "application/pdf", "url": "/10232/41/thesis_v1.pdf", "version": "v9.0.0" }, "type": "thesis", "title": "Localization and Stimulation Techniques for Implantable Medical Electronics", "author": [ { "family_name": "Monge Osorio", "given_name": "Manuel Alejandro", "orcid": "0000-0001-9799-0693", "clpid": "Monge-Osorio-Manuel-Alejandro" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "clpid": "Shapiro-M-G" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "clpid": "Shapiro-M-G" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Implantable medical devices (IMDs) are emerging as one of the keystones of tomorrow\u2019s medical technology. Although they have enabled a revolution in medicine, from research to diagnosis to treatment, most of today\u2019s devices have critical limitations. They are bulky, have low resolution, and, in some cases, are limited to basic functionality. Miniaturization of IMDs will have an enormous impact not only on the technology itself and the medical procedures they enable, but also on the lives of patients, who will be more comfortable, have greater confidence in their medical treatments, and enjoy an overall improvement in their quality of life. The path towards miniaturized bioelectronic devices requires a reevaluation of existing paradigms to reach a seamless integration of electronics and biology. Miniaturization of medical electronics then involves an exploration of advanced integrated circuit processes and novel circuit and system level architectures. In this dissertation, we provide an overview of implantable medical devices and present novel circuit and system level techniques for the miniaturization of medical electronics.
\r\n\r\nThe function of wireless miniaturized medical devices such as capsule endoscopes, biosensors, and drug delivery systems depends critically on their location inside the body. However, existing electromagnetic, acoustic, and imaging-based methods for localizing and communicating with such devices with spatial selectivity are limited by the physical properties of tissue or imaging modality performance. In the first part of this dissertation, we introduce a new approach for microscale device localization by embodying the principles of nuclear magnetic resonance in a silicon integrated circuit. By analogy to the behavior of nuclear spins, we engineer miniaturized RF transmitters that encode their location in space by shifting their output frequency in proportion to the local magnetic field. The application of external field gradients then allows each device\u2019s location to be determined precisely from the frequency of its signal. We demonstrate the core capabilities of these devices, which we call addressable transmitters operated as magnetic spins (ATOMS), in an integrated circuit smaller than 0.7 mm^3, manufactured through a standard 180 nm complementary metal-oxide-semiconductor (CMOS) process. We show that ATOMS are capable of sub-millimeter localization in vitro and in vivo. As a technology that is inherently robust to tissue properties and scalable to multiple devices, ATOMS localization provides an enabling capability for the development of microscale devices to monitor and treat disease.
\r\n\r\nIn neuroprosthetics, retinal prostheses aim to restore vision in patients suffering from advanced stages of retinal degeneration (e.g., retinitis pigmentosa) by bypassing the damaged photoreceptors and directly stimulating the remaining healthy neurons. In the second part of this dissertation, we describe a fully intraocular self-calibrating epiretinal prosthesis that reduces area and power consumption, and increases the functionality and resolution of traditional implementations. We introduce a novel novel digital calibration technique that matches the biphasic stimulation currents of each channel independently while sharing the calibration circuitry among every 4 channels. The system-on-chip presents dual-band telemetry for power and data with on-chip rectifier and clock recovery. These techniques reduce the number of off-chip components and achieve a power conversion efficiency >80% and supporting data rates up to 20 Mb/s. The system occupies an area of 4.5 x 3.1 mm2 and is implemented in 65 nm CMOS . It features 512 independent channels with a pixel size of 0.0169 mm2 and arbitrary waveform generation per channel. The chip is integrated with flexible MEMS origami coils and parylene substrate to provide a fully intraocular implant.
", "doi": "10.7907/Z9P55KJ7", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10178", "collection": "thesis", "collection_id": "10178", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05162017-205230203", "primary_object_url": { "basename": "Safaripour_Thesis.pdf", "content": "final", "filesize": 50078784, "license": "other", "mime_type": "application/pdf", "url": "/10178/19/Safaripour_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Proximal-Field Radiation Sensors for Dynamically Controllable and Self-Correcting Integrated Radiators", "author": [ { "family_name": "Safaripour Tabbalvandani", "given_name": "Amirreza", "orcid": "0000-0001-9758-6156", "clpid": "Safaripour-Tabbalvandani-Amirreza" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "One of the major challenges in the design of integrated radiators at mm-wave frequencies is the generation of surface waves in the dielectric substrate by the on-chip antennas. Since dielectric substrates are excellent surface waveguides with a fundamental mode with no cutoff frequency, there is always some energy trapped in them due to the surface waves and the excited substrate modes. This phenomenon is a significant cause of reduced radiation efficiency for mm-wave integrated radiators. However, in this thesis, we use this as an opportunity. We show that the excited substrate modes in the dielectric substrate of an integrated antenna contain valuable information regarding its far-field radiation properties. We introduce Proximal-Field Radiation Sensors (PFRS) as a number of small sensing antennas that are placed strategically on the same substrate as the integrated antenna and measure electromagnetic waves in its immediate proximity. These sensors extract the existing information in the substrate modes and use it to predict the far-field radiation properties of the integrated antenna in real-time based on in-situ measurements in the close proximity of the antennas, without any need to use additional test equipment and without removing the antenna from its operating environment or interfering with its operation in a wireless system. In other words, PFRS enables self-calibration, self-correction, and self-monitoring of the performance of the integrated antennas. Design intuition and a variety of data processing schemes for these sensors are discussed. Two proof-of-concept prototypes are fabricated on printed circuit board (PCB) and integrated circuit (IC) and both verify PFRS capabilities in prediction of radiation properties solely based on in-situ measurements.
\r\n\r\nDynamically controllable integrated radiators would significantly benefit from PFRS, These radiators are capable of controlling their radiation parameters such as polarization and beam steering angle through their actuators and control units. In these cases, PFRS serves as a tool for real-time monitoring of their radiation parameters, so that without direct measurement of the far-field properties through bulky equipment the required information for the control units and the actuators are provided.
\r\n\r\nDynamically controllable integrated radiators can be designed using the additional design space provided by Multi-Port Driven (MPD) radiator methodology. After a review of advantages of MPD design over the traditional single-port design, we show that a slot-based MPD radiator would have the additional advantage of reduced exclusive use area compared to the original wire-based MPD radiator, through demonstration of a 134.5-GHz integrated slot-based MPD radiator with a measured single-element EIRP of +6.0 dBm and a total radiated power of -1.3 dBm.
\r\n\r\nWe discuss how MPD methodology enables the new concept of Dynamic Polarization Control, as a method to ensure polarization matching of the transmitter antenna to the receiver antenna, regardless of the polarization and orientation of the receiver antenna in space. A DPC antenna design using the MPD methodology is described and a 105.5-GHz 2x1 integrated DPC radiator array with a maximum EIRP of +7.8 dBm and a total radiated power of 0.9 mW is presented as the first demonstration of an integrated radiator with DPC capability. This prototype can control the polarization angle across the entire tuning range of 0 to 180 degrees while maintaining axial ratios above 10 dB, and control the axial ratio from 2.4 dB (near circular) to 14 dB (linear). We also demonstrate how simultaneous two-dimensional beam steering and DPC capabilities can even match the polarization to a mobile receiver antenna through a prototype 123-GHz 2x2 integrated DPC radiator array with a maximum EIRP of +12.3 dBm, polarization angle control across the full range of 0to 180 degrees as well as tunable axial ratio down to 1.2 dB and beam steering of up to 15 degrees in both dimensions. We also use slot-based DPC antennas to fabricate a 120-GHz integrated slot-based DPC radiator array, expected to have a maximum EIRP of +15.5 dBm.
\r\n\r\nWe also introduce a new modulation scheme called Polarization Modulation (Pol-M) as a result of DPC capability, where the polarization itself is used for encoding the data. Pol-M is a spatial modulation method and is orthogonal to the existing phase and amplitude modulation schemes. Thus, it could be added on top of those schemes to enable creation of 4-D data constellations, or it can be used as the only basis for modulation to increase the stream security by misleading the undesired receivers. We discuss how DPC antenna enables Pol-M and also present PCB prototypes for Pol-M transmitter and receiver units operating at 2.4 GHz.
\r\n", "doi": "10.7907/Z9DR2SJZ", "publication_date": "2017", "thesis_type": "phd", "thesis_year": "2017" }, { "id": "thesis:10284", "collection": "thesis", "collection_id": "10284", "cite_using_url": "https://resolver.caltech.edu/CaltechThesis:06052017-131214880", "primary_object_url": { "basename": "Hong_Brian_Eng2017.pdf", "content": "final", "filesize": 5037212, "license": "other", "mime_type": "application/pdf", "url": "/10284/1/Hong_Brian_Eng2017.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Mathematical Modeling of Electronic Systems: From Oscillators to Multipliers", "author": [ { "family_name": "Hong", "given_name": "Brian Daffern", "orcid": "0000-0001-8099-0312", "clpid": "Hong-Brian-Daffern" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The ubiquity of electronics in modern technology is undeniable. Although it is not feasible to design or analyze circuits in an exhaustively detailed fashion, it is still imperative that circuit design engineers understand the pertinent physical tradeoffs and are able to think at the appropriate level of mathematical abstraction. This thesis presents several mathematical modeling techniques of common electronic systems.
\r\n\r\nFirst, we derive, ab initio, a general analytical model for the behavior of electrical oscillators under injection without making any assumptions about the type of oscillator or the size or shape of the injection. This model provides novel insights into the phenomena of injection locking and pulling while subsuming existing theories found in the literature. Next, we focus on the familiar scenario of an inductor-capacitor (LC) oscillator locked to a sinusoidal signal. An exact analysis of this circuit is carried out for an arbitrary injection strength and frequency, a task which has not been executed to fruition in the existing literature. This analysis intuitively illuminates the fundamental physics underlying the synchronization of electrical harmonic oscillators, and it generalizes the notion of the lock range for such oscillators into separate necessary and sufficient conditions. We then turn to the classical estimate of the bandwidth of a linear time-invariant (LTI) system via the sum of its zero-value time constants (ZVTs), and we show that this sum can actually be used to tightly bound the bandwidth\u2014both from above and from below\u2014in addition to simply estimating it. Finally, we look at a natural generalization of the Gilbert cell topology: an analog multiplier for an arbitrary number of inputs; we then analyze its large- and small-signal characteristics as well as its frequency response.
\r\n\r\nThroughout, we will demonstrate how infusing physical intuition with mathematical rigor whilst seeking a balance between detailed analysis and abstract modularity results in models that are conceptually insightful, sufficiently accurate, and computationally feasible.
", "doi": "10.7907/Z9RB72NG", "publication_date": "2017", "thesis_type": "engd", "thesis_year": "2017" }, { "id": "thesis:9234", "collection": "thesis", "collection_id": "9234", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10212015-150203289", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 109730024, "license": "other", "mime_type": "application/pdf", "url": "/9234/1/Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Holistic Design In High-Speed Optical Interconnects", "author": [ { "family_name": "Saeedi", "given_name": "Saman", "clpid": "Saeedi-Saman" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated circuit scaling has enabled a huge growth in processing capability, which necessitates a corresponding increase in inter-chip communication bandwidth. As bandwidth requirements for chip-to-chip interconnection scale, deficiencies of electrical channels become more apparent. Optical links present a viable alternative due to their low frequency-dependent loss and higher bandwidth density in the form of wavelength division multiplexing. As integrated photonics and bonding technologies are maturing, commercialization of hybrid-integrated optical links are becoming a reality. Increasing silicon integration leads to better performance in optical links but necessitates a corresponding co-design strategy in both electronics and photonics. In this light, holistic design of high-speed optical links with an in-depth understanding of photonics and state-of-the-art electronics brings their performance to unprecedented levels. This thesis presents developments in high-speed optical links by co-designing and co-integrating the primary elements of an optical link: receiver, transmitter, and clocking.
\r\n\r\nIn the first part of this thesis a 3D-integrated CMOS/Silicon-photonic receiver will be presented. The electronic chip features a novel design that employs a low-bandwidth TIA front-end, double-sampling and equalization through dynamic offset modulation. Measured results show -14.9dBm of sensitivity and energy efficiency of 170fJ/b at 25Gb/s. The same receiver front-end is also used to implement source-synchronous 4-channel WDM-based parallel optical receiver. Quadrature ILO-based clocking is employed for synchronization and a novel frequency-tracking method that exploits the dynamics of IL in a quadrature ring oscillator to increase the effective locking range. An adaptive body-biasing circuit is designed to maintain the per-bit-energy consumption constant across wide data-rates. The prototype measurements indicate a record-low power consumption of 153fJ/b at 32Gb/s. The receiver sensitivity is measured to be -8.8dBm at 32Gb/s.
\r\n\r\nNext, on the optical transmitter side, three new techniques will be presented. First one is a differential ring modulator that breaks the optical bandwidth/quality factor trade-off known to limit the speed of high-Q ring modulators. This structure maintains a constant energy in the ring to avoid pattern-dependent power droop. As a first proof of concept, a prototype has been fabricated and measured up to 10Gb/s. The second technique is thermal stabilization of micro-ring resonator modulators through direct measurement of temperature using a monolithic PTAT temperature sensor. The measured temperature is used in a feedback loop to adjust the thermal tuner of the ring. A prototype is fabricated and a closed-loop feedback system is demonstrated to operate at 20Gb/s in the presence of temperature fluctuations. The third technique is a switched-capacitor based pre-emphasis technique designed to extend the inherently low bandwidth of carrier injection micro-ring modulators. A measured prototype of the optical transmitter achieves energy efficiency of 342fJ/bit at 10Gb/s and the wavelength stabilization circuit based on the monolithic PTAT sensor consumes 0.29mW.
\r\n\r\nLastly, a first-order frequency synthesizer that is suitable for high-speed on-chip clock generation will be discussed. The proposed design features an architecture combining an LC quadrature VCO, two sample-and-holds, a PI, digital coarse-tuning, and rotational frequency detection for fine-tuning. In addition to an electrical reference clock, as an extra feature, the prototype chip is capable of receiving a low jitter optical reference clock generated by a high-repetition-rate mode-locked laser. The output clock at 8GHz has an integrated RMS jitter of 490fs, peak-to-peak periodic jitter of 2.06ps, and total RMS jitter of 680fs. The reference spurs are measured to be \u201364.3dB below the carrier frequency. At 8GHz the system consumes 2.49mW from a 1V supply.
", "doi": "10.7907/Z9K935HH", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:9779", "collection": "thesis", "collection_id": "9779", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05262016-210208370", "type": "thesis", "title": "Novel Parylene Filters for Biomedical Applications", "author": [ { "family_name": "Liu", "given_name": "Yang", "clpid": "Liu-Yang-Electrical-Engineering" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Shapiro", "given_name": "Mikhail G.", "clpid": "Shapiro-M-G" }, { "family_name": "Goldkorn", "given_name": "Amir", "clpid": "Goldkorn-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Medical engineering plays a more and more important role in driving the fundamental biology research moving forward. The work presented in this thesis targets at engineer smart parylene filters for various biomedical applications. Three novel parylene membranes are discussed. The first device is parylene magnesium-embedded filter for circulating tumor cells isolation. Circulating tumor cells (CTCs) are cells that slough off the edges of a primary tumor and are swept away by the bloodstream or lymphatic system into the vasculature. They constitute seeds for subsequent growth of additional tumors in vital distant organs, triggering a mechanism that is responsible for the vast majority of cancer-related deaths. Thus CTCs in peripheral blood have been investigated as a valuable biomarker for patients with various types of cancers. However, CTCs are difficult targets to probe owing to their extremely low concentration in peripheral blood. Although rare, CTCs represent a potential approach for the detection, characterization and monitoring of non-haematologic cancers. Therefore, CTCs capture from whole blood has been identified to be an unmet need for cancer research and effective cell separation methods are required to facilitate the study of CTCs. In this study, we developed a novel design applying a buried sacrificial Magnesium (Mg) layer underneath the original microfilter. After filtration, the filter was immersed in DMEM. When the thin-film Mg was dissolved, the cells were released and thus were ready for further biology analysis.
\r\n\r\nThe second device is parylene based microelectrode filter for single-islet electroisletogram. Other than direct insulin injection, one promising treatment for Type I diabetes is islet transplantation. However, one of the key lacking technologies of islet transplantation is high-throughput islet screening since each transplantation requires about one million islets. Islets, which are heterogeneous by nature, are currently screened as whole populations containing a range of functioning and dysfunctional characteristics. This work represents the first attempt to develop a MEMS technology for the screening of every single islet so as to guarantee no bad islet at all, which should improve results of islet transplant therapy. Here we report the first MEMS device designed for in vitro measuring of electroisletogram (EIG) of individual rat islets. Strong EIG signals in millivolt range are obtained. This work proves the feasibility of using MEMS and EIG for high-throughput screening, in contrast to patch-clamp measurements, of islets for transplantation to treat diabetes.
\r\n\r\nThe third device is parylene-on-PDMS membrane for vaccine production. A parylene-on-PDMS design is proposed to supply oxygen to CV-1 cells for vaccine production. Because the cells are seeded and attached right onto the surface of the device, extra oxygen is provided through permeation from the PDMS and thin parylene layers. The permeation is studied and cell growth experiments are performed to demonstrate the feasibility of the device. Compared to commercialized bioreactors, this novel design could have large cell density because oxygen are supplied locally and shear force is not a limiting factor any more.
\r\n\r\nBesides the three devices, parylene properties are also studied and a novel origami design is proposed, which can potentially increase the surface areas of the membranes by fold the 2D flat film into 3D structures. Details are discussed in the following chapters.
", "doi": "10.7907/Z97P8WDF", "publication_date": "2016", "thesis_type": "phd", "thesis_year": "2016" }, { "id": "thesis:8719", "collection": "thesis", "collection_id": "8719", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11062014-090236636", "type": "thesis", "title": "Injection Locked Clocking and Transmitter Equalization Techniques for Chip to Chip Interconnects", "author": [ { "family_name": "Raj", "given_name": "Mayank", "clpid": "Raj-Mayank" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Semiconductor technology scaling has enabled drastic growth in the computational capacity of integrated circuits (ICs). This constant growth drives an increasing demand for high bandwidth communication between ICs. Electrical channel bandwidth has not been able to keep up with this demand, making I/O link design more challenging. Interconnects which employ optical channels have negligible frequency dependent loss and provide a potential solution to this I/O bandwidth problem. Apart from the type of channel, efficient high-speed communication also relies on generation and distribution of multi-phase, high-speed, and high-quality clock signals. In the multi-gigahertz frequency range, conventional clocking techniques have encountered several design challenges in terms of power consumption, skew and jitter. Injection-locking is a promising technique to address these design challenges for gigahertz clocking. However, its small locking range has been a major contributor in preventing its ubiquitous acceptance.
\r\n \r\nIn the first part of this dissertation we describe a wideband injection locking scheme in an LC oscillator. Phase locked loop (PLL) and injection locking elements are combined symbiotically to achieve wide locking range while retaining the simplicity of the latter. This method does not require a phase frequency detector or a loop filter to achieve phase lock. A mathematical analysis of the system is presented and the expression for new locking range is derived. A locking range of 13.4 GHz\u201317.2 GHz (25%) and an average jitter tracking bandwidth of up to 400 MHz are measured in a high-Q LC oscillator. This architecture is used to generate quadrature phases from a single clock without any frequency division. It also provides high frequency jitter filtering while retaining the low frequency correlated jitter essential for forwarded clock receivers.
\r\n\r\nTo improve the locking range of an injection locked ring oscillator; QLL (Quadrature locked loop) is introduced. The inherent dynamics of injection locked quadrature ring oscillator are used to improve its locking range from 5% (7-7.4GHz) to 90% (4-11GHz). The QLL is used to generate accurate clock phases for a four channel optical receiver using a forwarded clock at quarter-rate. The QLL drives an injection locked oscillator (ILO) at each channel without any repeaters for local quadrature clock generation. Each local ILO has deskew capability for phase alignment. The optical-receiver uses the inherent frequency to voltage conversion provided by the QLL to dynamically body bias its devices. A wide locking range of the QLL helps to achieve a reliable data-rate of 16-32Gb/s and adaptive body biasing aids in maintaining an ultra-low power consumption of 153pJ/bit.
\r\n \r\nFrom the optical receiver we move on to discussing a non-linear equalization technique for a vertical-cavity surface-emitting laser (VCSEL) based optical transmitter, to enable low-power, high-speed optical transmission. A non-linear time domain optical model of the VCSEL is built and evaluated for accuracy. The modelling shows that, while conventional FIR-based pre-emphasis works well for LTI electrical channels, it is not optimum for the non-linear optical frequency response of the VCSEL. Based on the simulations of the model an optimum equalization methodology is derived. The equalization technique is used to achieve a data-rate of 20Gb/s with power efficiency of 0.77pJ/bit.
\r\n", "doi": "10.7907/Z90P0WZD", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8982", "collection": "thesis", "collection_id": "8982", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042015-065451017", "primary_object_url": { "basename": "MEMS for Diabetic Retinopathy_Dongyang_06122015_Final.pdf", "content": "final", "filesize": 15903015, "license": "other", "mime_type": "application/pdf", "url": "/8982/1/MEMS for Diabetic Retinopathy_Dongyang_06122015_Final.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "MEMS for Diabetic Retinopathy", "author": [ { "family_name": "Kang", "given_name": "Dongyang", "clpid": "Kang-Dongyang" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Humayun", "given_name": "Mark", "clpid": "Humayun-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "As the worldwide prevalence of diabetes mellitus continues to increase, diabetic retinopathy remains the leading cause of visual impairment and blindness in many developed countries. Between 32 to 40 percent of about 246 million people with diabetes develop diabetic retinopathy. Approximately 4.1 million American adults 40 years and older are affected by diabetic retinopathy. This glucose-induced microvascular disease progressively damages the tiny blood vessels that nourish the retina, the light-sensitive tissue at the back of the eye, leading to retinal ischemia (i.e., inadequate blood flow), retinal hypoxia (i.e., oxygen deprivation), and retinal nerve cell degeneration or death. It is a most serious sight-threatening complication of diabetes, resulting in significant irreversible vision loss, and even total blindness.
\r\n\r\nUnfortunately, although current treatments of diabetic retinopathy (i.e., laser therapy, vitrectomy surgery and anti-VEGF therapy) can reduce vision loss, they only slow down but cannot stop the degradation of the retina. Patients require repeated treatment to protect their sight. The current treatments also have significant drawbacks. Laser therapy is focused on preserving the macula, the area of the retina that is responsible for sharp, clear, central vision, by sacrificing the peripheral retina since there is only limited oxygen supply. Therefore, laser therapy results in a constricted peripheral visual field, reduced color vision, delayed dark adaptation, and weakened night vision. Vitrectomy surgery increases the risk of neovascular glaucoma, another devastating ocular disease, characterized by the proliferation of fibrovascular tissue in the anterior chamber angle. Anti-VEGF agents have potential adverse effects, and currently there is insufficient evidence to recommend their routine use.
\r\n\r\nIn this work, for the first time, a paradigm shift in the treatment of diabetic retinopathy is proposed: providing localized, supplemental oxygen to the ischemic tissue via an implantable MEMS device. The retinal architecture (e.g., thickness, cell densities, layered structure, etc.) of the rabbit eye exposed to ischemic hypoxic injuries was well preserved after targeted oxygen delivery to the hypoxic tissue, showing that the use of an external source of oxygen could improve the retinal oxygenation and prevent the progression of the ischemic cascade.
\r\n\r\nThe proposed MEMS device transports oxygen from an oxygen-rich space to the oxygen-deficient vitreous, the gel-like fluid that fills the inside of the eye, and then to the ischemic retina. This oxygen transport process is purely passive and completely driven by the gradient of oxygen partial pressure (pO2). Two types of devices were designed. For the first type, the oxygen-rich space is underneath the conjunctiva, a membrane covering the sclera (white part of the eye), beneath the eyelids and highly permeable to oxygen in the atmosphere when the eye is open. Therefore, sub-conjunctival pO2 is very high during the daytime. For the second type, the oxygen-rich space is inside the device since pure oxygen is needle-injected into the device on a regular basis.
\r\nTo prevent too fast or too slow permeation of oxygen through the device that is made of parylene and silicone (two widely used biocompatible polymers in medical devices), the material properties of the hybrid parylene/silicone were investigated, including mechanical behaviors, permeation rates, and adhesive forces. Then the thicknesses of parylene and silicone became important design parameters that were fine-tuned to reach the optimal oxygen permeation rate.
\r\n\r\nThe passive MEMS oxygen transporter devices were designed, built, and tested in both bench-top artificial eye models and in-vitro porcine cadaver eyes. The 3D unsteady saccade-induced laminar flow of water inside the eye model was modeled by computational fluid dynamics to study the convective transport of oxygen inside the eye induced by saccade (rapid eye movement). The saccade-enhanced transport effect was also demonstrated experimentally. Acute in-vivo animal experiments were performed in rabbits and dogs to verify the surgical procedure and the device functionality. Various hypotheses were confirmed both experimentally and computationally, suggesting that both the two types of devices are very promising to cure diabetic retinopathy. The chronic implantation of devices in ischemic dog eyes is still underway.
\r\nThe proposed MEMS oxygen transporter devices can be also applied to treat other ocular and systemic diseases accompanied by retinal ischemia, such as central retinal artery occlusion, carotid artery disease, and some form of glaucoma.
\r\n", "doi": "10.7907/Z97D2S34", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8994", "collection": "thesis", "collection_id": "8994", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06052015-084726649", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 3194374, "license": "other", "mime_type": "application/pdf", "url": "/8994/1/Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Microelectrode Implants for Spinal Cord Stimulation in Rats ", "author": [ { "family_name": "Nandra", "given_name": "Mandheerej Singh", "clpid": "Nandra-Mandheerej-Singh" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Edgerton", "given_name": "V. Reggie", "clpid": "Edgerton-V-R" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Paralysis is a debilitating condition afflicting millions of people across the globe, and is particularly deleterious to quality of life when motor function of the legs is severely impaired or completely absent. Fortunately, spinal cord stimulation has shown great potential for improving motor function after spinal cord injury and other pathological conditions. Many animal studies have shown stimulation of the neural networks in the spinal cord can improve motor ability so dramatically that the animals can even stand and step after a complete spinal cord transaction.
\r\n\r\nThis thesis presents work to successfully provide a chronically implantable device for rats that greatly enhances the ability to control the site of spinal cord stimulation. This is achieved through the use of a parylene-C based microelectrode array, which enables a density of stimulation sites unattainable with conventional wire electrodes. While many microelectrode devices have been proposed in the past, the spinal cord is a particularly challenging environment due to the bending and movement it undergoes in a live animal. The developed microelectrode array is the first to have been implanted in vivo while retaining functionality for over a month. In doing so, different neural pathways can be selectively activated to facilitate standing and stepping in spinalized rats using various electrode combinations, and important differences in responses are observed.
\r\n\r\nAn engineering challenge for the usability of any high density electrode array is connecting the numerous electrodes to a stimulation source. This thesis develops several technologies to address this challenge, beginning with a fully passive implant that uses one wire per electrode to connect to an external stimulation source. The number of wires passing through the body and the skin proved to be a hazard for the health of the animal, so a multiplexed implant was devised in which active electronics reduce the number of wires. Finally, a fully wireless implant was developed. As these implants are tested in vivo, encapsulation is of critical importance to retain functionality in a chronic experiment, especially for the active implants, and it was achieved without the use of costly ceramic or metallic hermetic packaging. Active implants were built that retained functionality 8 weeks after implantation, and achieved stepping in spinalized rats after just 8-10 days, which is far sooner than wire-based electrical stimulation has achieved in prior work.
", "doi": "10.7907/Z9930R3G", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:8717", "collection": "thesis", "collection_id": "8717", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10282014-113257585", "primary_object_url": { "basename": "KaushikThesis.pdf", "content": "final", "filesize": 22700825, "license": "other", "mime_type": "application/pdf", "url": "/8717/1/KaushikThesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Self-Healing Techniques for RF and mm-Wave Transmitters and Receivers", "author": [ { "family_name": "Dasgupta", "given_name": "Kaushik", "clpid": "Dasgupta-Kaushik" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "With continuing advances in CMOS technology, feature sizes of modern Silicon chip-sets have gone down drastically over the past decade. In addition to desktops and laptop processors, a vast majority of these chips are also being deployed in mobile communication devices like smart-phones and tablets, where multiple radio-frequency integrated circuits (RFICs) must be integrated into one device to cater to a wide variety of applications such as Wi-Fi, Bluetooth, NFC, wireless charging, etc. While a small feature size enables higher integration levels leading to billions of transistors co-existing on a single chip, it also makes these Silicon ICs more susceptible to variations. A part of these variations can be attributed to the manufacturing process itself, particularly due to the stringent dimensional tolerances associated with the lithographic steps in modern processes. Additionally, RF or millimeter-wave communication chip-sets are subject to another type of variation caused by dynamic changes in the operating environment. Another bottleneck in the development of high performance RF/mm-wave Silicon ICs is the lack of accurate analog/high-frequency models in nanometer CMOS processes. This can be primarily attributed to the fact that most cutting edge processes are geared towards digital system implementation and as such there is little model-to-hardware correlation at RF frequencies.
\r\n\r\nAll these issues have significantly degraded yield of high performance mm-wave and RF CMOS systems which often require multiple trial-and-error based Silicon validations, thereby incurring additional production costs. This dissertation proposes a low overhead technique which attempts to counter the detrimental effects of these variations, thereby improving both performance and yield of chips post fabrication in a systematic way. The key idea behind this approach is to dynamically sense the performance of the system, identify when a problem has occurred, and then actuate it back to its desired performance level through an intelligent on-chip optimization algorithm. We term this technique as self-healing drawing inspiration from nature's own way of healing the body against adverse environmental effects. To effectively demonstrate the efficacy of self-healing in CMOS systems, several representative examples are designed, fabricated, and measured against a variety of operating conditions.
\r\n\r\nWe demonstrate a high-power mm-wave segmented power mixer array based transmitter architecture that is capable of generating high-speed and non-constant envelope modulations at higher efficiencies compared to existing conventional designs. We then incorporate several sensors and actuators into the design and demonstrate closed-loop healing against a wide variety of non-ideal operating conditions. We also demonstrate fully-integrated self-healing in the context of another mm-wave power amplifier, where measurements were performed across several chips, showing significant improvements in performance as well as reduced variability in the presence of process variations and load impedance mismatch, as well as catastrophic transistor failure. Finally, on the receiver side, a closed-loop self-healing phase synthesis scheme is demonstrated in conjunction with a wide-band voltage controlled oscillator to generate phase shifter local oscillator (LO) signals for a phased array receiver. The system is shown to heal against non-idealities in the LO signal generation and distribution, significantly reducing phase errors across a wide range of frequencies.
", "doi": "10.7907/Z9HQ3WTR", "publication_date": "2015", "thesis_type": "phd", "thesis_year": "2015" }, { "id": "thesis:7988", "collection": "thesis", "collection_id": "7988", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10102013-145125571", "primary_object_url": { "basename": "BowersThesis_Oct9_2013.pdf", "content": "final", "filesize": 11580240, "license": "other", "mime_type": "application/pdf", "url": "/7988/1/BowersThesis_Oct9_2013.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Dynamically Controllable Integrated Radiation and Self-Correcting Power Generation in mm-Wave Circuits and Systems", "author": [ { "family_name": "Bowers", "given_name": "Steven Michael", "clpid": "Bowers-Steven-Michael" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Vahala", "given_name": "Kerry J.", "clpid": "Vahala-K-J" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents novel design methodologies for integrated radiators and power generation at mm-wave frequencies that are enabled by the continued integration of various electronic and electromagnetic (EM) structures onto the same substrate. Beginning with the observation that transistors and their connections to EM radiating structures on an integrated substrate are essentially free, the concept of multi-port driven (MPD) radiators is introduced, which opens a vast design space that has been generally ignored due to the cost structure associated with discrete components that favors fewer transistors connected to antennas through a single port.
\r\n\r\nFrom Maxwell's equations, a new antenna architecture, the radial MPD antennas based on the concept of MPD radiators, is analyzed to gain intuition as to the important design parameters that explain the wide-band nature of the antenna itself. The radiator is then designed and implemented at 160 GHz in a 0.13 um SiGe BiCMOS process, and the single element design has a measured effective isotropic radiated power (EIRP) of +4.6 dBm with a total radiated power of 0.63 mW.
\r\n\r\nNext, the radial MPD radiator is adapted to enable dynamic polarization control (DPC). A DPC antenna is capable of controlling its radiated polarization dynamically, and entirely electronically, with no mechanical reconfiguration required. This can be done by having multiple antennas with different polarizations, or within a single antenna that has multiple drive points, as in the case of the MPD radiator with DPC. This radiator changes its polarization by adjusting the relative phase and amplitude of its multiple ports to produce polarizations with any polarization angle, and a wide range of axial ratios. A 2x1 MPD radiator array with DPC at 105 GHz is presented whose measurements show control of the polarization angle throughout the entire 0 degree through 180 degree range while in the linear polarization mode and maintaining axial ratios above 10 dB in all cases. Control of the axial ratio is also demonstrated with a measured range from 2.4 dB through 14 dB, while maintaining a fixed polarization angle. The radiator itself has a measured maximum EIRP of +7.8 dBm, with a total radiated power of 0.9 mW, and is capable of beam steering.
\r\n \r\nMPD radiators were also applied in the domain of integrated silicon photonics. For these designs, the driver transistor circuitry was replaced with silicon optical waveguides and photodiodes to produce a 350 GHz signal. Three of these optical MPD radiator designs have been implemented as 2x2 arrays at 350 GHz. The first is a beam forming array that has a simulated gain of 12.1 dBi with a simulated EIRP of -2 dBm. The second has the same simulated performance, but includes optical phase modulators that enable two-dimensional beam steering. Finally, a third design incorporates multi-antenna DPC by combining the outputs of both left and right handed circularly polarized MPD antennas to produce a linear polarization with controllable polarization angle, and has a simulated gain of 11.9 dBi and EIRP of -3 dBm. In simulation, it can tune the polarization from 0 degrees through 180 degrees while maintaining a radiated power that has a 0.35 dB maximum deviation from the mean.
\r\n\r\nThe reliability of mm-wave radiators and power amplifiers was also investigated, and two self-healing systems have been proposed. Self-healing is a global feedback method where integrated sensors detect the performance of the circuit after fabrication and report that data to a digital control algorithm. The algorithm then is capable of setting actuators that can control the performance of the mm-wave circuit and counteract any performance degradation that is observed by the sensors. The first system is for a MPD radiator array with a partially integrated self-healing system. The self-healing MPD radiator senses substrate modes through substrate mode pickup sensors and infers the far-field radiated pattern from those sensors. DC current sensors are also included to determine the DC power consumption of the system. Actuators are implemented in the form of phase and amplitude control of the multiple drive points.
\r\n\r\nThe second self-healing system is a fully integrated self-healing power amplifier (PA) at 28 GHz. This system measures the output power, gain and efficiency of the PA using radio frequency (RF) power sensors, DC current sensors and junction temperature sensors. The digital block is synthesized from VHDL code on-chip and it can actuate the output power combining matching network using tunable transmission line stubs, as well as the DC operating point of the amplifying transistors through bias control. Measurements of 20 chips confirm self-healing for two different algorithms for process variation and transistor mismatch, while measurements from 10 chips show healing for load impedance mismatch, and linearity healing. Laser induced partial and total transistor failure show the benefit of self-healing in the case of catastrophic failure, with improvements of up to 3.9 dB over the default case. An exemplary yield specification shows self-healing improving the yield from 0% up through 80%.
", "doi": "10.7907/Z9MP518K", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7925", "collection": "thesis", "collection_id": "7925", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08172013-192316055", "primary_object_url": { "basename": "Sean_Keller_PhD_Thesis_2014.pdf", "content": "final", "filesize": 5183773, "license": "other", "mime_type": "application/pdf", "url": "/7925/1/Sean_Keller_PhD_Thesis_2014.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Robust Near-Threshold QDI Circuit Analysis and Design", "author": [ { "family_name": "Keller", "given_name": "Sean Jason", "clpid": "Keller-Sean-Jason" } ], "thesis_advisor": [ { "family_name": "Martin", "given_name": "Alain J.", "clpid": "Martin-A-J" } ], "thesis_committee": [ { "family_name": "Martin", "given_name": "Alain J.", "clpid": "Martin-A-J" }, { "family_name": "Wierman", "given_name": "Adam C.", "clpid": "Wierman-A-C" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Harris", "given_name": "David Money", "clpid": "Harris-D-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The two most important digital-system design goals today are to reduce power consumption and to increase reliability. Reductions in power consumption improve battery life in the mobile space and reductions in energy lower operating costs in the datacenter. Increased robustness and reliability shorten down time, improve yield, and are invaluable in the context of safety-critical systems. While optimizing towards these two goals is important at all design levels, optimizations at the circuit level have the furthest reaching effects; they apply to all digital systems. This dissertation presents a study of robust minimum-energy digital circuit design and analysis. It introduces new device models, metrics, and methods of calculation\u2014all necessary first steps towards building better systems\u2014and demonstrates how to apply these techniques. It analyzes a fabricated chip (a full-custom QDI microcontroller designed at Caltech and taped-out in 40-nm silicon) by calculating the minimum energy operating point and quantifying the chip\u2019s robustness in the face of both timing and functional failures.", "doi": "10.7907/79EJ-Q945", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7930", "collection": "thesis", "collection_id": "7930", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08202013-193131878", "primary_object_url": { "basename": "HanChieh_Chang_2013_thesis.pdf", "content": "final", "filesize": 26640127, "license": "other", "mime_type": "application/pdf", "url": "/7930/1/HanChieh_Chang_2013_thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Wireless Parylene-Based Retinal Implant", "author": [ { "family_name": "Chang", "given_name": "Jan Han-Chieh", "clpid": "Chang-Jan-Han-Chieh" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Weiland", "given_name": "James D.", "clpid": "Weiland-J-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The degeneration of the outer retina usually causes blindness by affecting the photoreceptor cells. However, the ganglion cells, which consist of optic nerves, on the middle and inner retina layers are often intact. The retinal implant, which can partially restore vision by electrical stimulation, soon becomes a focus for research. Although many groups worldwide have spent a lot of effort on building devices for retinal implant, current state-of-the-art technologies still lack a reliable packaging scheme for devices with desirable high-density multi-channel features. Wireless flexible retinal implants have always been the ultimate goal for retinal prosthesis. In this dissertation, the reliable packaging scheme for a wireless flexible parylene-based retinal implants has been well developed. It can not only provide stable electrical and mechanical connections to the high-density multi-channel (1000+ channels on 5 mm \u00d7 5 mm chip area) IC chips, but also survive for more than 10 years in the human body with corrosive fluids.
\r\n\r\nThe device is based on a parylene-metal-parylene sandwich structure. In which, the adhesion between the parylene layers and the metals embedded in the parylene layers have been studied. Integration technology for high-density multi-channel IC chips has also been addressed and tested with dummy and real 268-channel and 1024-channel retinal IC chips. In addition, different protection schemes have been tried in application to IC chips and discrete components to gain the longest lifetime. The effectiveness has been confirmed by the accelerated and active lifetime soaking test in saline solution. Surgical mockups have also been designed and successfully implanted inside dog's and pig's eyes. Additionally, the electrodes used to stimulate the ganglion cells have been modified to lower the interface impedance and shaped to better fit the retina. Finally, all the developed technologies have been applied on the final device with a dual-metal-layer structure.
\r\n", "doi": "10.7907/YTN7-ZA05", "publication_date": "2014", "thesis_type": "phd", "thesis_year": "2014" }, { "id": "thesis:7705", "collection": "thesis", "collection_id": "7705", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05142013-075702623", "type": "thesis", "title": "Parylene-C as a New Piezoelectric Material", "author": [ { "family_name": "Kim", "given_name": "Justin Young-Hyun", "clpid": "Kim-Justin-Young-Hyun" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The goal of this thesis is to develop a proper microelectromechanical systems (MEMS) process to manufacture piezoelectric Parylene-C (PA-C), which is famous for its chemical inertness, mechanical and thermal properties and electrical insulation. Furthermore, piezoelectric PA-C is used to build miniature, inexpensive, non-biased piezoelectric microphones.
\r\n \r\nThese piezoelectric PA-C MEMS microphones are to be used in any application where a conventional piezoelectric and electret microphone can be used, such as in cell phones and hearing aids. However, they have the advantage of a simplified fabrication process compared with existing technology. In addition, as a piezoelectric polymer, PA-C has varieties of applications due to its low dielectric constant, low elastic stiffness, low density, high voltage sensitivity, high temperature stability and low acoustic and mechanical impedance. Furthermore, PA-C is an FDA approved biocompatible material and is able to maintain operate at a high temperature.
\r\n\r\nTo accomplish piezoelectric PA-C, a MEMS-compatible poling technology has been developed. The PA-C film is poled by applying electrical field during heating. The piezoelectric coefficient, -3.75pC/N, is obtained without film stretching.
\r\n\r\nThe millimeter-scale piezoelectric PA-C microphone is fabricated with an in-plane spiral arrangement of two electrodes. The dynamic range is from less than 30 dB to above 110 dB SPL (referenced 20 \u00b5Pa) and the open-circuit sensitivities are from 0.001 \u2013 0.11 mV/Pa over a frequency range of 1 - 10 kHz. The total harmonic distortion of the device is less than 20% at 110 dB SPL and 1 kHz.
", "doi": "10.7907/1VEH-EP90", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7675", "collection": "thesis", "collection_id": "7675", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05082013-113725728", "primary_object_url": { "basename": "loh_rui_yan_matthew_2013_thesis.pdf", "content": "final", "filesize": 9062229, "license": "other", "mime_type": "application/pdf", "url": "/7675/1/loh_rui_yan_matthew_2013_thesis.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Dense, Efficient Chip-to-Chip Communication at the Extremes of Computing", "author": [ { "family_name": "Loh Rui Yan", "given_name": "Matthew", "clpid": "Loh-Rui-Yan-Matthew" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The scalability of CMOS technology has driven computation into a diverse range of applications across the power consumption, performance and size spectra. Communication is a necessary adjunct to computation, and whether this is to push data from node-to-node in a high-performance computing cluster or from the receiver of wireless link to a neural stimulator in a biomedical implant, interconnect can take up a significant portion of the overall system power budget. Although a single interconnect methodology cannot address such a broad range of systems efficiently, there are a number of key design concepts that enable good interconnect design in the age of highly-scaled CMOS: an emphasis on highly-digital approaches to solving \u2018analog\u2019 problems, hardware sharing between links as well as between different functions (such as equalization and synchronization) in the same link, and adaptive hardware that changes its operating parameters to mitigate not only variation in the fabrication of the link, but also link conditions that change over time. These concepts are demonstrated through the use of two design examples, at the extremes of the power and performance spectra.
\r\n\r\nA novel all-digital clock and data recovery technique for high-performance, high density interconnect has been developed. Two independently adjustable clock phases are generated from a delay line calibrated to 2 UI. One clock phase is placed in the middle of the eye to recover the data, while the other is swept across the delay line. The samples produced by the two clocks are compared to generate eye information, which is used to determine the best phase for data recovery. The functions of the two clocks are swapped after the data phase is updated; this ping-pong action allows an infinite delay range without the use of a PLL or DLL. The scheme's generalized sampling and retiming architecture is used in a sharing technique that saves power and area in high-density interconnect. The eye information generated is also useful for tuning an adaptive equalizer, circumventing the need for dedicated adaptation hardware.
\r\n\r\nOn the other side of the performance/power spectra, a capacitive proximity interconnect has been developed to support 3D integration of biomedical implants. In order to integrate more functionality while staying within size limits, implant electronics can be embedded onto a foldable parylene (\u2018origami\u2019) substrate. Many of the ICs in an origami implant will be placed face-to-face with each other, so wireless proximity interconnect can be used to increase communication density while decreasing implant size, as well as facilitate a modular approach to implant design, where pre-fabricated parylene-and-IC modules are assembled together on-demand to make custom implants. Such an interconnect needs to be able to sense and adapt to changes in alignment. The proposed array uses a TDC-like structure to realize both communication and alignment sensing within the same set of plates, increasing communication density and eliminating the need to infer link quality from a separate alignment block. In order to distinguish the communication plates from the nearby ground plane, a stimulus is applied to the transmitter plate, which is rectified at the receiver to bias a delay generation block. This delay is in turn converted into a digital word using a TDC, providing alignment information.
\r\n", "doi": "10.7907/FQ18-2X96", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7614", "collection": "thesis", "collection_id": "7614", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:04132013-185824588", "primary_object_url": { "basename": "Pang_Shuo_Thesis.pdf", "content": "final", "filesize": 12182996, "license": "other", "mime_type": "application/pdf", "url": "/7614/1/Pang_Shuo_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Fluorescence Optofluidic Microscopy and Fluorescence Microscopy Based on the Talbot Effect", "author": [ { "family_name": "Pang", "given_name": "Shuo", "clpid": "Pang-Shuo" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Sternberg", "given_name": "Paul W.", "clpid": "Sternberg-P-W" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Light microscopy has been one of the most common tools in biological research, because of its high resolution and non-invasive nature of the light. Due to its high sensitivity and specificity, fluorescence is one of the most important readout modes of light microscopy. This thesis presents two new fluorescence microscopic imaging techniques: fluorescence optofluidic microscopy and fluorescent Talbot microscopy. The designs of the two systems are fundamentally different from conventional microscopy, which makes compact and portable devices possible. The components of the devices are suitable for mass-production, making the microscopic imaging system more affordable for biological research and clinical diagnostics.
\r\n\r\nFluorescence optofluidic microscopy (FOFM) is capable of imaging fluorescent samples in fluid media. The FOFM employs an array of Fresnel zone plates (FZP) to generate an array of focused light spots within a microfluidic channel. As a sample flows through the channel and across the array of focused light spots, a filter-coated CMOS sensor collects the fluorescence emissions. The collected data can then be processed to render a fluorescence microscopic image. The resolution, which is determined by the focused light spot size, is experimentally measured to be 0.65 \u03bcm.
\r\n\r\nFluorescence Talbot microscopy (FTM) is a fluorescence chip-scale microscopy technique that enables large field-of-view (FOV) and high-resolution imaging. The FTM method utilizes the Talbot effect to project a grid of focused excitation light spots onto the sample. The sample is placed on a filter-coated CMOS sensor chip. The fluorescence emissions associated with each focal spot are collected by the sensor chip and are composed into a sparsely sampled fluorescence image. By raster scanning the Talbot focal spot grid across the sample and collecting a sequence of sparse images, a filled-in high-resolution fluorescence image can be reconstructed. In contrast to a conventional microscope, a collection efficiency, resolution, and FOV are not tied to each other for this technique. The FOV of FTM is directly scalable. Our FTM prototype has demonstrated a resolution of 1.2 \u03bcm, and the collection efficiency equivalent to a conventional microscope objective with a 0.70 N.A. The FOV is 3.9 mm \u00d7 3.5 mm, which is 100 times larger than that of a 20X/0.40 N.A. conventional microscope objective. Due to its large FOV, high collection efficiency, compactness, and its potential for integration with other on-chip devices, FTM is suitable for diverse applications, such as point-of-care diagnostics, large-scale functional screens, and long-term automated imaging.
", "doi": "10.7907/WWFF-7S14", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7286", "collection": "thesis", "collection_id": "7286", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:11262012-212534634", "primary_object_url": { "basename": "DSRussell_Thesis_2012.pdf", "content": "final", "filesize": 16046459, "license": "other", "mime_type": "application/pdf", "url": "/7286/1/DSRussell_Thesis_2012.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Technology Advances for Radio Astronomy", "author": [ { "family_name": "Russell", "given_name": "Damon Stuart", "clpid": "Russell-Damon-Stuart" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Weinreb", "given_name": "Sander", "orcid": "0000-0002-9353-6204", "clpid": "Weinreb-S" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "orcid": "0000-0001-6736-8019", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Readhead", "given_name": "Anthony C. S.", "orcid": "0000-0001-9152-961X", "clpid": "Readhead-A-C-S" }, { "family_name": "Gaier", "given_name": "Todd C.", "clpid": "Gaier-T-C" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The field of radio astronomy continues to provide fundamental contributions to the understanding of the evolution, and inner workings of, our universe. It has done so from its humble beginnings, where single antennas and receivers were used for observation, to today's focal plane arrays and interferometers. The number of receiving elements (pixels) in these instruments is quickly growing, currently approaching one hundred. For the instruments of tomorrow, the number of receiving elements will be in the thousands. Such instruments will enable researchers to peer deeper into the fabric of our universe and do so at faster survey speeds. They will provide enormous capability, both for unraveling today's mysteries as well as for the discovery of new phenomena.
\r\n \r\nAmong other challenges, producing the large numbers of low-noise amplifiers required for these instruments will be no easy task. The work described in this thesis advances the state of the art in three critical areas, technological advancements necessary for the future design and manufacturing of thousands of low-noise amplifiers. These areas being: the automated, cryogenic, probing of $\\diameter100$ mm indium phosphide wafers; a system for measuring the noise parameters of devices at cryogenic temperatures; and the development of low-noise, silicon germanium amplifiers for terahertz mixer receivers. The four chapters that comprise the body of this work detail the background, design, assembly, and testing involved in these contributions. Also included is a brief survey of noise parameters, the knowledge of which is fundamental to the design of low-noise amplifiers and the optimization of the system noise temperature for large, dense, interferometers.
", "doi": "10.7907/MW3P-2S22", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7226", "collection": "thesis", "collection_id": "7226", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10072012-230900231", "primary_object_url": { "basename": "Nikil-Mehta-2013.pdf", "content": "final", "filesize": 1724373, "license": "other", "mime_type": "application/pdf", "url": "/7226/1/Nikil-Mehta-2013.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "An Ultra-Low-Energy, Variation-Tolerant FPGA Architecture Using Component-Specific Mapping", "author": [ { "family_name": "Mehta", "given_name": "Nikil", "clpid": "Mehta-Nikil" } ], "thesis_advisor": [ { "family_name": "DeHon", "given_name": "Andre", "clpid": "DeHon-A" } ], "thesis_committee": [ { "family_name": "Martin", "given_name": "Alain J.", "clpid": "Martin-A-J" }, { "family_name": "DeHon", "given_name": "Andre", "clpid": "DeHon-A" }, { "family_name": "Calhoun", "given_name": "Benton H.", "clpid": "Calhoun-B-H" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "As feature sizes scale toward atomic limits, parameter variation continues to increase, leading to increased margins in both delay and energy. Parameter variation both slows down devices and causes devices to fail. For applications that require high performance, the possibility of very slow devices on critical paths forces designers to reduce clock speed in order to meet timing. For an important and emerging class of applications that target energy-minimal operation at the cost of delay, the impact of variation-induced defects at very low voltages mandates the sizing up of transistors and operation at higher voltages to maintain functionality.
\r\n\r\nWith post-fabrication configurability, FPGAs have the opportunity to self-measure the impact of variation, determining the speed and functionality of each individual resource. Given that information, a delay-aware router can use slow devices on non-critical paths, fast devices on critical paths, and avoid known defects. By mapping each component individually and customizing designs to a component's unique physical characteristics, we demonstrate that we can eliminate delay margins and reduce energy margins caused by variation.
\r\n\r\nTo quantify the potential benefit we might gain from component-specific mapping, we first measure the margins associated with parameter variation, and then focus primarily on the energy benefits of FPGA delay-aware routing over a wide range of predictive technologies (45 nm--12 nm) for the Toronto20 benchmark set. We show that relative to delay-oblivious routing, delay-aware routing without any significant optimizations can reduce minimum energy/operation by 1.72x at 22 nm. We demonstrate how to construct an FPGA architecture specifically tailored to further increase the minimum energy savings of component-specific mapping by using the following techniques: power gating, gate sizing, interconnect sparing, and LUT remapping. With all optimizations considered we show a minimum energy/operation savings of 2.66x at 22 nm, or 1.68--2.95x when considered across 45--12 nm. As there are many challenges to measuring resource delays and mapping per chip, we discuss methods that may make component-specific mapping more practical. We demonstrate that a simpler, defect-aware routing achieves 70% of the energy savings of delay-aware routing. Finally, we show that without variation tolerance, scaling from 16 nm to 12 nm results in a net increase in minimum energy/operation; component-specific mapping, however, can extend minimum energy/operation scaling to 12 nm and possibly beyond.
\r\n", "doi": "10.7907/358S-CW22", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7762", "collection": "thesis", "collection_id": "7762", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05282013-164038057", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 19208500, "license": "other", "mime_type": "application/pdf", "url": "/7762/1/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Electrical and Optical Interconnects for High-Performance Computing", "author": [ { "family_name": "Honarvar Nazari", "given_name": "Meisam", "clpid": "Honarvar-Nazari-Meisam" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Technology scaling has enabled drastic growth in the computational and storage capacity of integrated circuits (ICs). This constant growth drives an increasing demand for high-bandwidth communication between and within ICs. In this dissertation we focus on low-power solutions that address this demand. We divide communication links into three subcategories depending on the communication distance. Each category has a different set of challenges and requirements and is affected by CMOS technology scaling in a different manner. We start with short-range chip-to-chip links for board-level communication. Next we will discuss board-to-board links, which demand a longer communication range. Finally on-chip links with communication ranges of a few millimeters are discussed.
\r\n\r\nElectrical signaling is a natural choice for chip-to-chip communication due to efficient integration and low cost. IO data rates have increased to the point where electrical signaling is now limited by the channel bandwidth. In order to achieve multi-Gb/s data rates, complex designs that equalize the channel are necessary. In addition, a high level of parallelism is central to sustaining bandwidth growth. Decision feedback equalization (DFE) is one of the most commonly employed techniques to overcome the limited bandwidth problem of the electrical channels. A linear and low-power summer is the central block of a DFE. Conventional approaches employ current-mode techniques to implement the summer, which require high power consumption. In order to achieve low-power operation we propose performing the summation in the charge domain. This approach enables a low-power and compact realization of the DFE as well as crosstalk cancellation. A prototype receiver was fabricated in 45nm SOI CMOS to validate the functionality of the proposed technique and was tested over channels with different levels of loss and coupling. Measurement results show that the receiver can equalize channels with maximum 21dB loss while consuming about 7.5mW from a 1.2V supply. We also introduce a compact, low-power transmitter employing passive equalization. The efficacy of the proposed technique is demonstrated through implementation of a prototype in 65nm CMOS. The design achieves up to 20Gb/s data rate while consuming less than 10mW.
\r\n \r\nAn alternative to electrical signaling is to employ optical signaling for chip-to-chip interconnections, which offers low channel loss and cross-talk while providing high communication bandwidth. In this work we demonstrate the possibility of building compact and low-power optical receivers. A novel RC front-end is proposed that combines dynamic offset modulation and double-sampling techniques to eliminate the need for a short time constant at the input of the receiver. Unlike conventional designs, this receiver does not require a high-gain stage that runs at the data rate, making it suitable for low-power implementations. In addition, it allows time-division multiplexing to support very high data rates. A prototype was implemented in 65nm CMOS and achieved up to 24Gb/s with less than 0.4pJ/b power efficiency per channel. As the proposed design mainly employs digital blocks, it benefits greatly from technology scaling in terms of power and area saving.
\r\n\r\nAs the technology scales, the number of transistors on the chip grows. This necessitates a corresponding increase in the bandwidth of the on-chip wires. In this dissertation, we take a close look at wire scaling and investigate its effect on wire performance metrics. We explore a novel on-chip communication link based on a double-sampling architecture and dynamic offset modulation technique that enables low power consumption and high data rates while achieving high bandwidth density in 28nm CMOS technology. The functionality of the link is demonstrated using different length minimum-pitch on-chip wires. Measurement results show that the link achieves up to 20Gb/s of data rate (12.5Gb/s/$\\mu$m) with better than 136fJ/b of power efficiency.
", "doi": "10.7907/TSX2-EE48", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7902", "collection": "thesis", "collection_id": "7902", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06172013-155313179", "primary_object_url": { "basename": "Thesis_JianRen_2013.pdf", "content": "final", "filesize": 20121522, "license": "other", "mime_type": "application/pdf", "url": "/7902/13/Thesis_JianRen_2013.pdf", "version": "v11.0.0" }, "type": "thesis", "title": "Endoscopic Optical Coherence Tomography: Design and Application", "author": [ { "family_name": "Ren", "given_name": "Jian", "clpid": "Ren-Jian" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Humayun", "given_name": "Mark", "clpid": "Humayun-M" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents an investigation on endoscopic optical coherence tomography (OCT). As a noninvasive imaging modality, OCT emerges as an increasingly important diagnostic tool for many clinical applications. Despite of many of its merits, such as high resolution and depth resolvability, a major limitation is the relatively shallow penetration depth in tissue (about 2\u223c3 mm). This is mainly due to tissue scattering and absorption. To overcome this limitation, people have been developing many different endoscopic OCT systems. By utilizing a minimally invasive endoscope, the OCT probing beam can be brought to the close vicinity of the tissue of interest and bypass the scattering of intervening tissues so that it can collect the reflected light signal from desired depth and provide a clear image representing the physiological structure of the region, which can not be disclosed by traditional OCT. In this thesis, three endoscope designs have been studied. While they rely on vastly different principles, they all converge to solve this long-standing problem.
\r\n\r\nA hand-held endoscope with manual scanning is first explored. When a user is holding a hand- held endoscope to examine samples, the movement of the device provides a natural scanning. We proposed and implemented an optical tracking system to estimate and record the trajectory of the device. By registering the OCT axial scan with the spatial information obtained from the tracking system, one can use this system to simply \u2018paint\u2019 a desired volume and get any arbitrary scanning pattern by manually waving the endoscope over the region of interest. The accuracy of the tracking system was measured to be about 10 microns, which is comparable to the lateral resolution of most OCT system. Targeted phantom sample and biological samples were manually scanned and the reconstructed images verified the method.
\r\n\r\nNext, we investigated a mechanical way to steer the beam in an OCT endoscope, which is termed as Paired-angle-rotation scanning (PARS). This concept was proposed by my colleague and we further developed this technology by enhancing the longevity of the device, reducing the diameter of the probe, and shrinking down the form factor of the hand-piece. Several families of probes have been designed and fabricated with various optical performances. They have been applied to different applications, including the collector channel examination for glaucoma stent implantation, and vitreous remnant detection during live animal vitrectomy.
\r\n\r\nLastly a novel non-moving scanning method has been devised. This approach is based on the EO effect of a KTN crystal. With Ohmic contact of the electrodes, the KTN crystal can exhibit a special mode of EO effect, termed as space-charge-controlled electro-optic effect, where the carrier electron will be injected into the material via the Ohmic contact. By applying a high voltage across the material, a linear phase profile can be built under this mode, which in turn deflects the light beam passing through. We constructed a relay telescope to adapt the KTN deflector into a bench top OCT scanning system. One of major technical challenges for this system is the strong chromatic dispersion of KTN crystal within the wavelength band of OCT system. We investigated its impact on the acquired OCT images and proposed a new approach to estimate and compensate the actual dispersion. Comparing with traditional methods, the new method is more computational efficient and accurate. Some biological samples were scanned by this KTN based system. The acquired images justified the feasibility of the usage of this system into a endoscopy setting.\r\nMy research above all aims to provide solutions to implement an OCT endoscope. As technology evolves from manual, to mechanical, and to electrical approaches, different solutions are presented. Since all have their own advantages and disadvantages, one has to determine the actual requirements and select the best fit for a specific application.
", "doi": "10.7907/Z9445JF5", "publication_date": "2013", "thesis_type": "phd", "thesis_year": "2013" }, { "id": "thesis:7163", "collection": "thesis", "collection_id": "7163", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06122012-144158047", "primary_object_url": { "basename": "JuhwanYoo-thesis-update.pdf", "content": "updated", "filesize": 5048489, "license": "other", "mime_type": "application/pdf", "url": "/7163/2/JuhwanYoo-thesis-update.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Compressed Sensing Receivers: Theory, Design, and Performance Limits", "author": [ { "family_name": "Yoo", "given_name": "Juhwan", "clpid": "Yoo-Juhwan" } ], "thesis_advisor": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Candes", "given_name": "Emmanuel J.", "clpid": "Candes-E-J" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" }, { "family_name": "Tropp", "given_name": "Joel A.", "clpid": "Tropp-J-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The past 50 years have seen tremendous developments in electronics due to the rise and rapid development of IC-fabrication technology [1]. In addition to the production of cheap and abundant computing resources, another area of rapid advancement has been wireless technologies. While the central focus of wireless research has been mobile communication, an area of increasing importance concerns the development of sensing/spectral applications over bandwidths exceeding multiple GHz. Such systems have many applications ranging from scientific to military. Although some solutions exist, their large size, weight, and power make more-efficient solutions desirable.
\r\n\r\nAt present, one of the principal bottlenecks in designing such systems is the power consumption of the back-end ADCs at the required digitization rate. ADCs are a dominant source of power consumption; it is also often the case that ADC block specifications are used to determine parameters for the rest of the signal chain, such as the RF front-end and the DSP-core which processes the digitized samples [2]. Historically, increases in system bandwidth have come from developing ADCs with superior performance.
\r\n\r\nIn contrast to improving ADC performance, this work presents a system-level approach with the goal of minimizing the required digitization rate for observation of a given effective instantaneous bandwidth (EIBW). The approach was inspired by the field of compressed sensing [3\u20135]. Loosely stated, CS asserts that samples which represent random projections can be used to recover sparse and/or compressible signals with what was previously thought to be insufficient information. The primary contributions of this thesis include: the establishment of physical feasibility of CS-based receivers through implementation of the first fully-integrated high speed CS-based front-end known as the random-modulation pre-integrator (RMPI) [6\u20139], and the development of a principled design methodology based on a rigorous analytical and empirical feasibility study of the system.
\r\n\r\nThe 8-channel RMPI was implemented in 90 nm CMOS and was validated by physical measurements of the fabricated chip. The implemented RMPI achieves an EIBW of 2 GHz, with > 54 dB of dynamic range. Most notably, the aggregate digitization rate is fs = 320 Msps, 12.5\u00d7 lower than the Nyquist rate.
\r\n\r\n", "doi": "10.7907/Y3FA-VB87", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7130", "collection": "thesis", "collection_id": "7130", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06042012-135440197", "primary_object_url": { "basename": "Full_Thesis-v5.pdf", "content": "final", "filesize": 16190173, "license": "other", "mime_type": "application/pdf", "url": "/7130/1/Full_Thesis-v5.pdf", "version": "v6.0.0" }, "type": "thesis", "title": "Biomimetic Accommodating Intraocular Lens", "author": [ { "family_name": "DeBoer", "given_name": "Charles Meno Theodore", "clpid": "DeBoer-Charles-Meno-Theodore" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Humayun", "given_name": "Mark", "clpid": "Humayun-M" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The crystalline lens allows the eye to focus on near and far objects. During the aging process, it loses its ability to focus and often becomes cloudy during cataract formation. At this point, traditional medical therapy replaces the lens with an artificial replacement lens. Although replacement lenses for the crystalline lens have been implanted since 1949 for cataract surgery, none of the FDA-approved lenses mimic the anatomy of the natural lens. Hence, they are not able to focus in a manner similar to the youthful lens. Instead, they function in a manner similar to the aged lens and only provide vision at a single distance or at a very limited range of focal distances. Patients with the newest implants are often obliged to use reading glasses when using near vision, or suffer from optical aberrations, halos, or glare. Therefore, there is a need to provide youthful vision after lens surgery in terms of focusing ability, accurate optical power, and sharp focus without distortion or optical aberrations.
\r\n\r\nThis thesis presents an approach to restoring youthful vision after lens replacement. An intraocular lens (IOL) that can provide accurate visual acuity along with focusing ability is proposed. This IOL relies on the natural anatomy and physiology of the eye, and therefore is actuated in a manner identical to the natural lens. In addition, the lens has the capability for adjustment during or after implantation to provide high-acuity vision throughout life.
\r\n\r\nThe natural anatomy and physiology of the eye is described, along with lens replacement surgery. A lens design is proposed to address the unmet need of lens-replacement patients. Specific care in the design is made for small surgical incisions, high visual acuity, adjustable acuity over years, and the ability to focus similar to the natural lens. Methods to test the IOL using human donor tissue are developed based upon prior experiments on the ex vivo natural lens. These tools are used to demonstrate efficacy of the newly developed accommodating intraocular lens.
\r\n\r\nTo further demonstrate implant feasibility, materials and processes for building the lens are evaluated for biocompatibility, endurance, repeatable manufacture, and stability. The lens biomechanics are determined after developing an artificial anatomy testing setup inspired by the natural anatomy of the human focusing mechanism. Finally, based upon a mechanical and optical knowledge of the lens, several improved lens concepts are proposed and demonstrated for efficacy.
", "doi": "10.7907/Z9B56GQH", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6765", "collection": "thesis", "collection_id": "6765", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01082012-184435123", "primary_object_url": { "basename": "Bohn_Thesis_edit2_export.pdf", "content": "final", "filesize": 4637504, "license": "other", "mime_type": "application/pdf", "url": "/6765/1/Bohn_Thesis_edit2_export.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Integrated Circuit Signal Generation and Detection Techniques for Microwave and Sub-Millimeter Wave Signals", "author": [ { "family_name": "Bohn", "given_name": "Florian", "clpid": "Bohn-Florian" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Chattopadhyay", "given_name": "Goutam", "clpid": "Chattopadhyay-G" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The unabated reduction of device feature sizes in semiconductor processes, particularly in complementary metal-oxide semiconductor (CMOS) processes, has served as the enabling factor behind integrated electronic systems of ever increasing complexity and speeds. As a result, former niche market applications, such as the global-positioning system (GPS), cellular telephony or powerful general purpose computers, have expanded into the field of consumer electronics with tremendous impact on the daily lives of millions of people. It is, therefore, only logical that the future will bring new applications to the mass market that today only exist as niche applications.\r\nSystems operating in the millimeter wave frequency range are an example of a current niche market, with current research striving to fully integrate such systems using advanced semiconductor processing technology. Electromagnetic waves at these frequencies become comparable in size to the electronics circuits. This opens the possibility for novel design approaches that were traditionally not available to integrated circuit radio-frequency designers. On the other hand, the increase in the number of available devices also brings with it new challenges due to increasing variability in device performance. Self-correcting techniques for integrated circuits that offset this increased variability are therefore also highly desirable.
\r\n\r\nIn this dissertation, we explore the above issues on several fronts. We will first present a phase-locked loop synthesizer that auto-corrects its spurious output tones as an example of circuits that correct for a parasitic effect by leveraging the availability of many active devices to construct a digital feedback loop. We will then focus on the effort to operate CMOS integrated circuits in the terahertz regime by developing a solid design foundation for converting signals to frequencies beyond the maximum power gain frequency\u3016 f\u3017_max. We will use the insights gained to develop and explore two designs generating power at these high frequencies as proofs of concept. Finally, we will focus on the passive electromagnetic components of such high frequency systems and present a novel way of designing electromagnetic structures that are comparable to the wavelength size in integrated systems by introducing the third physical dimension into the design process for integrated electromagnetic structures.
\r\n", "doi": "10.7907/Q018-QP18", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6719", "collection": "thesis", "collection_id": "6719", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:10192011-190918785", "primary_object_url": { "basename": "Thesis_Lap_Man_Lee.pdf", "content": "final", "filesize": 4822758, "license": "other", "mime_type": "application/pdf", "url": "/6719/1/Thesis_Lap_Man_Lee.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "The Implementation of Optofluidic Microscopy on a Chip Scale and Its Potential Applications in Biology", "author": [ { "family_name": "Lee", "given_name": "Lap Man", "clpid": "Lee-Lap-Man" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Guo", "given_name": "Chin-Lin", "clpid": "Guo-Chin-Lin" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents an effort to miniaturize conventional optical microscopy to a chip level using microfluidic technology. Modern compound microscopes use a set of bulk glass lenses to form magnified images from biological objects. This limits the possibility of shrinking the size of a microscope system. The invention of micro/nanofabrication technology gives hope to engineers who want to rethink the way we build optical microscopes. This advancement can fundamentally reform the way clinicians and biologists conduct microscopy. Optofluidic microscopy (OFM) is a miniaturized optical imaging method which utilizes a microfluidic flow to deliver biological samples across a 1-D or 2-D array of sampling points defined in a microfluidic channel for optical scanning. The optical information of these sampling points is collected by a CMOS imaging sensor on the bottom of the microfluidic channel. Although the size of the OFM device is as small as a US dime, it can render high resolution images of less than 1 \u03bcm with quality comparable to that of a bulky, standard optical microscope. OFM has a good potential in various biological applications. For example, the integration of an OFM system with high-speed hydrodynamic focusing technology will allow very large scale imaging-based analysis of cells or microorganisms; the compactness and low cost nature of OFM systems can enable portable or even disposable biomedical diagnostic tools for future telemedicine and personalized health care. ", "doi": "10.7907/GKW9-QR51", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7053", "collection": "thesis", "collection_id": "7053", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05192012-003206031", "primary_object_url": { "basename": "MEMS_for_Glaucoma_Lin_2012.pdf", "content": "final", "filesize": 7792333, "license": "other", "mime_type": "application/pdf", "url": "/7053/1/MEMS_for_Glaucoma_Lin_2012.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "MEMS for Glaucoma", "author": [ { "family_name": "Lin", "given_name": "Jeffrey Chun-Hui", "clpid": "Lin-Jeffrey-Chun-Hui" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Glaucoma is an eye disease that gradually steals vision. Open angle glaucoma is one of the most common glaucoma forms, in which eye fluid (aqueous humor) produced by the ciliary body cannot be drained away normally by patients\u2019 eyes. The accumulated eye fluid inside the anterior chamber causes high intraocular pressure (IOP), which is transmitted onto the retina in the back of the eyeball (globe), continuously suppressing and damaging the patient\u2019s optic nerves; this may lead to total blindness if not treated properly.
\r\n\r\nThe current most-popular IOP monitoring technique is to use applanation tonometry, which applies applanation force onto the cornea and measures the resulting deformation in order to calculate the IOP. Even though applanation tonometry can provide quite useful information about patients\u2019 IOP, continuous monitoring of IOP is required for ophthalmologists to understand the IOP fluctuation of the patients, something which still cannot be achieved via current applanation approach. In addition, applanation tonometry requires skillful operation performed by well-trained professionals, such as ophthalmologists, making continuous IOP monitoring impractical. In this work, we have developed a telemetric IOP sensor that is capable of monitoring IOP wirelessly and continuously. As the quality factor drops when a telemetric IOP sensor is implanted in the anterior chamber, due to the high loss tangent of the saline-based aqueous humor (~ 0.2) compared to air (0.0), a modified IOP sensor is developed to monitor IOP with sensing coil that is left exposed after implantation in order to avoid interruption from the eye fluid. Another approach is also proposed and tested to demonstrate that the quality factor can also be recovered by covering the sensing coil with low loss tangent materials.
\r\n\r\nCurrently glaucoma is treated mostly by taking oral medications or applying eye drops. However, some glaucoma patients do not respond to those medications. Therefore, another physical approach, using a glaucoma drainage device (GDD), is necessary in order to drain out excessive eye fluid and serve as a long-term way to manage the increased IOP. Current commercially available glaucoma drainage devices do not have reliable valve systems to stop the drainage when the IOP falls into the normal range. Therefore, we have developed a dual-valved GDD to fulfill the \u201cband-pass\u201d flow regulation which drains out eye fluid only when IOP is higher than 20 mmHg, and stops drainage (closes the valve) when IOP is lower than 20 mmHg to prevent hypotony. The key component of GDD is a normally closed (NC) check-valve, which only opens to drain away the excess fluid when the pressure is higher than 20 mmHg. The proposed paradigm of our NC check-valve is to have a couple of parylene-C pre-stressed slanted tethers to provide the desired cracking pressure. The slanted tethers are achieved in this thesis by: 1) slanted photoresist generated by gray-scale photolithography, 2) pop-up mechanism, and 3) self-stiction bonding mechanism. The built-in residual tensile stress can be controlled by mechanical stretching or thermal annealing. The protecting mechanism preventing the unwanted drainage when the eyes experience sudden unpredicted high IOP is achieved by utilizing a normally open (NO) check-valve. A \"minimally invasive implantation\" procedure is proposed in the thesis to implant the GDD subconjunctivally. The small size of the device allows its insertion using a #19-gauge needle.
\r\n\r\nTo accurately design the desired cracking pressure and also predict the lifetime of the NC check-valve, parylene-C\u2019s mechanical, thermal, and polymer properties are investigated. The results show that the properties of parylene-C are highly process-temperature-dependent and therefore can be tailored by adjusting the thermal annealing process.
", "doi": "10.7907/4XD2-SP34", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:7158", "collection": "thesis", "collection_id": "7158", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06112012-145654043", "type": "thesis", "title": "Silicon-Based Terahertz Circuits and Systems", "author": [ { "family_name": "Sengupta", "given_name": "Kaushik", "clpid": "Sengupta-Kaushik" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Choo", "given_name": "Hyuck", "clpid": "Choo-Hyuck" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Terahertz frequency range, often referred to as the `Terahertz' gap, lies wedged between microwave at the lower end and infrared at the higher end of the spectrum, occupying frequencies between 0.3-3.0 THz. For a long time, applications in THz frequencies had been limited to astronomy and chemical sciences, but with advancement in THz technology in recent years, it has shown great promise in a wide range of applications ranging from disease diagnostics, non-invasive early skin cancer detection, label-free DNA sequencing to security screening for concealed weapons and contraband detection, global environmental monitoring, nondestructive quality control and ultra-fast wireless communication. Up until recently, the terahertz frequency range has been mostly addressed by high mobility compound III-V processes, expensive nonlinear optics, or cryogenically cooled quantum cascade lasers. A low cost, room temperature alternative can enable the development of such a wide array of applications, not currently accessible due to cost and size limitations. In this thesis, we will discuss our approach towards development of integrated terahertz technology in silicon-based processes. In the spirit of academic research, we will address frequencies close to 0.3 THz as 'Terahertz'.
\r\n\r\nIn this thesis, we address both fronts of integrated THz systems in silicon: THz power generation, radiation and transmitter systems, and THz signal detection and receiver systems. THz power generation in silicon-based integrated circuit technology is challenging due to lower carrier mobility, lower cut-o frequencies compared to compound III-V processes, lower breakdown voltages and lossy passives. Radiation from silicon chip is also challenging due to lossy substrates and high dielectric constant of silicon. In this work, we propose novel ways of combining circuit and electromagnetic techniques in a holistic design approach, which can overcome limitations of conventional block-by-block or partitioned design methodology, in order to generate high-frequency signals above the classical definition of cut-off frequencies (\u0192t/\u0192max). We demonstrate this design philosophy in an active electromagnetic structure, which we call Distributed Active Radiator. It is inspired by an Inverse\r\nMaxwellian approach, where instead of using classical circuit and electromagnetic blocks to generate and radiate THz frequencies, we formulate surface (metal) currents in silicon chip for a desired THz field prole and develop active means of controlling different harmonic\r\ncurrents to perform signal generation, frequency multiplication, radiation and lossless filtering, simultaneously in a compact footprint. By removing the articial boundaries between circuits, electromagnetics and antenna, we open ourselves to a broader design space. This\r\nenabled us to demonstrate the rst 1 mW Eective-isotropic-radiated-power(EIRP) THz (0.29 THz) source in CMOS with total radiated power being three orders of magnitude more than previously demonstrated. We also proposed a near-field synchronization mechanism, which is a scalable method of realizing large arrays of synchronized autonomous radiating sources in silicon. We also demonstrate the first THz CMOS array with digitally controlled beam-scanning in 2D space with radiated output EIRP of nearly 10 mW at 0.28 THz.
\r\n\r\nOn the receiver side, we use a similar electronics and electromagnetics co-design approach to realize a 4x4 pixel integrated silicon Terahertz camera demonstrating to the best of our knowledge, the most sensitive silicon THz detector array without using post-processing,\r\nsilicon lens or high-resistivity substrate options (NEP < 10 pW √ Hz at 0.26 THz). We put the 16 pixel silicon THz camera together with the CMOS DAR THz power generation arrays and demonstrated, for the first time, an all silicon THz imaging system with a CMOS source.
", "doi": "10.7907/MBXB-6R29", "publication_date": "2012", "thesis_type": "phd", "thesis_year": "2012" }, { "id": "thesis:6005", "collection": "thesis", "collection_id": "6005", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08232010-071647727", "type": "thesis", "title": "Techniques for Mixed-Signal Linearization and Large Signal Handling in Radio-Frequency Receiver Circuits", "author": [ { "family_name": "Keehr", "given_name": "Edward Arthur", "clpid": "Keehr-Edward-Arthur" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" }, { "family_name": "D'Addario", "given_name": "Larry R.", "clpid": "D'Addario-L-R" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In this dissertation, two effective linearization schemes for radio-frequency receivers are introduced. The first of these comprises a mixed-signal feedforward path which regenerates third-order intermodulation (IM3) products at radio frequencies, downconverts these products, digitizes them, and then uses them to cancel corruptive IM3 products in the digital baseband portion of a nominally linear receiver path. The combined implemented receiver represents a SAW-less direct-conversion receiver for UMTS FDD Region 1 that achieves an uncorrected out-of-band IIP3 of -7.1dBm under worst-case blocking specifications. Under IM3 equalization, the receiver achieves an effective IIP3 of +5.3dBm and meets the UMTS BER sensitivity requirements with 3.7dB of margin. To enable this mixed-signal feedforward path, a multistage cubic term generator is introduced which uses cascaded nonlinear operations to generate reference IM3 products. The multistage nature of this circuit is considered in the context of the aforementioned linearization scheme and is shown to provide sufficient dynamic range for nearly complete IM3 cancellation while dissipating far less power than the original receiver front end. In particular, the effect of the group delay between stages is analyzed and shown to permit large IM3 cancellation ratios for interstage group delays less than 1ns.
\r\n\r\nExpanding upon the first effective linearization approach led to the development of a large signal handling receiver with an out-of-band 1-dB desensitization point of +12.5dBm. Enabling this large signal handling capability is a passive mixer downconverter preceded by a novel wide-swing LNTA. With a stacked push-pull class-AB common-gate architecture, the LNTA reduces the magnitude of input-referred distortion by up to 40dB beyond that predicted by an initial slope-of-3 characteristic while at the same time minimally impacting the effective small-signal gain of the receiver. To compensate for intermodulation distortion terms of order greater than 3, IM3 and IM2 products are processed down to digital baseband where they are successively multiplied to generate approximations to higher-order terms. In the case of a +12.4dBm QPSK-modulated signal and a -16.3dBm CW blocker, cancellation improves receiver input-referred error by over 24dB, resulting in an extrapolated IIP3 of +43.5dBm.
", "doi": "10.7907/WFGT-4823", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5970", "collection": "thesis", "collection_id": "5970", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:07092010-104142755", "primary_object_url": { "basename": "Ray_Huang_PhD_Thesis.pdf", "content": "final", "filesize": 5798296, "license": "other", "mime_type": "application/pdf", "url": "/5970/1/Ray_Huang_PhD_Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Flexible Neural Implants", "author": [ { "family_name": "Huang", "given_name": "Ray Kui-Jui", "clpid": "Huang-Ray-Kui-Jui" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Andersen", "given_name": "Richard A.", "clpid": "Andersen-R-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Despite recent development in integration technologies for biomedical implantable devices, current state-of-the-art prosthetic platforms still lack a reliable and convenient packaging scheme to integrate high-density signal-driving chips, wireless telemetry circuitries and noise-canceling amplifiers, mainly due to the limitations in fabrication technology, material compatibility and interconnect reliability. In this dissertation, new packaging technologies are developed and presented to enable a new generation of flexible neural implants. These technologies can also house integrated circuit chips and provide high-density electrical connection to it.
\r\n\r\nThis packaging scheme utilizes the parylene-metal-parylene skin structure and can be totally integrated and be monolithically fabricated with existing functional devices. The size and the electrode patterns can be modified to suit different chips and applications. Integration with flexible cable integrated silicon probes for neural prosthesis, implantable muscle stimulators and implantable RFID tagging technology are all successfully demonstrated in this dissertation. Other discrete components can also be integrated to achieve high level functionality.
\r\n\r\nIn order to ensure the long-term stability of such packaging scheme, accelerated hot saline soaking test is conducted on the overall structure and its components. Detailed adhesion enhancement techniques are also presented to improve its performances. A physical model of the flexible retinal implant is then tested in vivo during the course of the experiment. Finally, the high-density squeegee bonding technique is introduced, which allows the integration of a 256-channel chip. Functionality of the chip has been demonstrated. As a result, this technology has the potential to achieve ultra high lead count connection and can facilitate future research in flexible implantable biodevices.
\r\n", "doi": "10.7907/VMZB-0N20", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6492", "collection": "thesis", "collection_id": "6492", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022011-152525054", "primary_object_url": { "basename": "thesis.pdf", "content": "final", "filesize": 8891944, "license": "other", "mime_type": "application/pdf", "url": "/6492/1/thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Practical Compressed Sensing: Modern Data Acquisition and Signal Processing", "author": [ { "family_name": "Becker", "given_name": "Stephen R.", "orcid": "0000-0002-1932-8159", "clpid": "Becker-Stephen-R" } ], "thesis_advisor": [ { "family_name": "Candes", "given_name": "Emmanuel J.", "clpid": "Candes-E-J" } ], "thesis_committee": [ { "family_name": "Candes", "given_name": "Emmanuel J.", "clpid": "Candes-E-J" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Tropp", "given_name": "Joel A.", "clpid": "Tropp-J-A" }, { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" }, { "family_name": "Vandenberghe", "given_name": "Lieven", "clpid": "Vandenberghe-L" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Since 2004, the field of compressed sensing has grown quickly and seen tremendous interest because it provides a theoretically sound and computationally tractable method to stably recover signals by sampling at the information rate. This thesis presents in detail the design of one of the world's first compressed sensing hardware devices, the random modulation pre-integrator (RMPI). The RMPI is an analog-to-digital converter (ADC) that bypasses a current limitation in ADC technology and achieves an unprecedented 8 effective number of bits over a bandwidth of 2.5 GHz. Subtle but important design considerations are discussed, and state-of-the-art reconstruction techniques are presented.
\r\n\r\nInspired by the need for a fast method to solve reconstruction problems for the RMPI, we develop two efficient large-scale optimization methods, NESTA and TFOCS, that are applicable to a wide range of other problems, such as image denoising and deblurring, MRI reconstruction, and matrix completion (including the famous Netflix problem). While many algorithms solve unconstrained l1 problems, NESTA and TFOCS can solve the constrained form of l1 minimization, and allow weighted norms. In addition to l1 minimization problems such as the LASSO, both NESTA and TFOCS solve total-variation minimization problem. TFOCS also solves the Dantzig selector and most variants of the nuclear norm minimization problem. A common theme in both NESTA and TFOCS is the use of smoothing techniques, which make the problem tractable, and the use of optimal first-order methods that have an accelerated convergence rate yet have the same cost per iteration as gradient descent. The conic dual methodology is introduced in TFOCS and proves to be extremely flexible, covering such generic problems as linear programming, quadratic programming, and semi-definite programming. A novel continuation scheme is presented, and it is shown that the Dantzig selector benefits from an exact-penalty property. Both NESTA and TFOCS are released as software packages available freely for academic use.
", "doi": "10.7907/DC16-K322", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:6222", "collection": "thesis", "collection_id": "6222", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:01102011-204907918", "primary_object_url": { "basename": "Electrolytic_Inchworms.pdf", "content": "final", "filesize": 12433844, "license": "other", "mime_type": "application/pdf", "url": "/6222/1/Electrolytic_Inchworms.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "MEMS Electrolytic Inchworms for Movable Neural Probe Applications", "author": [ { "family_name": "Giacchino", "given_name": "Luca", "clpid": "Giacchino-Luca" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" }, { "family_name": "Kornfield", "given_name": "Julia A.", "clpid": "Kornfield-J-A" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Over decades of cortical neural prosthesis, it was found that \"movable\" neural probes are important to track neurons for long-term, reliable prostheses. This is challenging because the ideal movable probes require low voltage, small power, bidirectional/latchable movement, and large total traveling distance. The device should also be small enough to entirely fit under the skull after implantation. Many different devices have been demonstrated to move neural probes, but none of them satisfies all the actuation and size requirements.
\r\n\r\nThis thesis presents our work on actuators for movable neural probes that combine MEMS technology with an electrolytic actuation mechanism. Each inchworm is based on two electrolytic balloon actuators. The actuators rely on gas generation by electrolysis inside a sealed balloon, which causes its expansion. When electrolysis is stopped, gas recombination and permeation across the balloon membrane cause the balloon to relax. Electrolytic actuation, although slow, has several advantages: low power, low voltage, and ability to provide large force and displacement. The balloons have been characterized and their behavior mathematically modeled. Innovative salt-shell-based and hydrogel-based processes have been developed to fabricate the balloons and to allow their replenishment by osmosis.
\r\n\r\nTwo balloons are combined into a bidirectional inchworm mechanism. Large traveling distance can be obtained in multiple cycles, the only constraint being the probe length. Displacement of a silicon probe and of a commercial metal probe have been demonstrated in both directions, with a displacement per cycle between 0.5 um and 75 um. The voltage required to drive electrolysis is typically around 3.5 V, with peak power per balloon around 100 uW. The devices were tested in air, water, and saline.
\r\n\r\nClosed-loop control of the inchworm may be needed for accurate positioning of the probe, and monitoring of the pressure inside the balloons represents a possible source of feedback from the inchworm. Parylene-membrane pressure sensors that are suitable for integration inside balloon actuators have been demonstrated.
", "doi": "10.7907/GQYY-BM80", "publication_date": "2011", "thesis_type": "phd", "thesis_year": "2011" }, { "id": "thesis:5233", "collection": "thesis", "collection_id": "5233", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06102009-164232", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 10103965, "license": "other", "mime_type": "application/pdf", "url": "/5233/1/Thesis.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Precision Frequency and Phase Synthesis Techniques in Integrated Circuits for Biosensing, Communication and Radar", "author": [ { "family_name": "Wang", "given_name": "Hua", "orcid": "0000-0003-4952-5505", "clpid": "Wang-Hua" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Today\u2019s CMOS technology provides circuit designers with a powerful implementation platform that supports innovation opportunities on both circuit-topology and system-architecture levels. Moreover, the versatility of CMOS implementation opens the door for a plethora of challenging and exciting interdisciplinary research.
\r\n\r\nThis dissertation focuses on investigating novel techniques and applications for precision frequency and phase synthesis in CMOS. It consists of two parts: a CMOS compatible molecular-level biosensor and a multiple-beam/multi-band scalable CMOS phased array receiver system.
\r\n\r\nIn the first part, a frequency shift based magnetic biosensing scheme is introduced to address the Point-of-Care (PoC) biomolecular diagnosis for high-sensitivity, portable and cost low applications. Compared with existing biosensing schemes, the proposed scheme achieves a competitive sensitivity without using optical devices, external biasing fields or expensive post-processing steps. A discrete implementation first verifies the sensing mechanism and reveals several design insights. An integrated implementation based on standard 130nm CMOS process is then designed with differential sensing and temperature controlling schemes. Overall, with a differential uncertainty of 0.13ppm for relative frequency shift, the sensor achieves reliable detection of one single micron-size magnetic particle (D=4.5um, 2.4um and 1um) as well as 1n-Molar real DNA samples labeled by magnetic nanoparticles (D=50nm).
\r\n\r\nIn the second part, a high-resolution compensation technique is proposed to address mismatch and offset issues encountered by practical phased array system. It employs a dense Cartesian interpolation scheme with an easily scalable architecture and a wide operation bandwidth. As an implementation example, a 6-to-18GHz dual-band quad-beam phased array CMOS receiver is presented, which is capable of forming four spatially independent beams at two different frequencies across the tritave bandwidth. With the mismatch compensation, the array element has achieved a maximum RMS phase error of 0.5\u02da with an RMS amplitude variation less than 1.5dB for the 360\u02da interpolation over the full operation bandwidth. For a 4-element phased array receiver system based on the designed CMOS chip, the electrical array pattern is measured at 6GHz, 10.4GHz and 18GHz, with the worst case peak-to-null ratio of 21.5dB. In addition, a broadband inductorless design methodology based on Cherry-Hooper topology is proposed for chip area saving. As implementation examples, we will show a DC-19GHz 10dB gain broadband buffer amplifier, a DC-12GHz broadband phase rotator with 10-bit resolution and a beam-forming network in a 10.4GHz to 18GHz phased array receiver chip with dual-beam capability.
", "doi": "10.7907/T4EC-TX97", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:648", "collection": "thesis", "collection_id": "648", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-02162009-095558", "primary_object_url": { "basename": "Dissertation_Wen.pdf", "content": "final", "filesize": 9878128, "license": "other", "mime_type": "application/pdf", "url": "/648/1/Dissertation_Wen.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Integrated Retinal Implants", "author": [ { "family_name": "Li", "given_name": "Wen", "clpid": "Li-Wen" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Weiland", "given_name": "James D.", "clpid": "Weiland-J-D" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Integrated wireless implants have always been the ultimate goal for neural prostheses. However, technologies are still in development and few have actually been transferred to clinical practice due to constraints in material biocompatibility, device miniaturization and flexibility. In this dissertation, emphasis is placed on the development of Parylene devices for neural prostheses, and particularly, for retinal prostheses that partially restore lost vision for patients suffering from outer retina degeneration.
\r\n\r\nA basic Parylene-metal-Parylene skin technology for making planar Parylene micro-electro-mechanical systems (MEMS) devices, such as electrode arrays and radio-frequency (RF) coil, is first discussed, followed by accelerated lifetime soaking tests to investigate the long term stability of such skins in hot saline under both passive and active electrical stressing. Discussion is further expanded on a detailed description of the design, fabrication, and testing procedure of two types of MEMS coils, which serve as receiver coils for wireless power and data transfer in a retinal implant system. After that, an embedded chip integration technology is presented, which allows the integration of complementary metal-oxide-semiconductor (CMOS) integrated circuit (IC) chips with other MEMS devices and discrete components so as to achieve high-level system functionality. Finally, an integrated wireless neural stimulator is designed and successfully fabricated using a test chip.
\r\n", "doi": "10.7907/AMK6-TA42", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:5179", "collection": "thesis", "collection_id": "5179", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03292009-070752", "primary_object_url": { "basename": "Thesis-yujiu-final-20090331.pdf", "content": "final", "filesize": 3325286, "license": "other", "mime_type": "application/pdf", "url": "/5179/1/Thesis-yujiu-final-20090331.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Circuits and Systems for Wireless Concurrent Communication", "author": [ { "family_name": "Wang", "given_name": "Yu-Jiu", "orcid": "0000-0002-2534-1069", "clpid": "Wang-Yu-Jiu" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Concurrency is a special kind of analog circuit parallelism that uses a single circuit with necessary bandwidth to process multiple signals at the same time. Concurrent radios offer a higher data rate and improved system diversity. Our comprehensive treatment comprises proposals for potential transceiver architectures, invention of circuit blocks, and provisions of innovative analysis methods.
\r\n\r\nThe analysis of concurrent circuits are often complex. To simplify noise analysis, a R^(N^2 )-vector space is first proposed to re-formulate the N-port network noise modeling problem. Any internal physical source inside the noisy network contributes a small vector in the defined R^(N^2)-vector space, and the aggregate statistical behavior of this noisy network can be viewed as the vector sum of these vectors. Applying this concept to FET noise modeling leads to several modified FET noise models, in which three uncorrelated noise sources are sufficient to describe the statistical behavior of an intrinsic FET. The use of these new FET models can simplify the analysis, simulation, and optimization of low noise systems without sacrificing accuracy.
\r\n\r\nBroadband low-noise amplifier is a critical block in concurrent receiver systems. We propose a novel low-noise weighted distributed amplifier (WDA) topology, which uses the internal finite-impulse-response filtering inside a conventional distributed amplifier to partially suppress internal thermal noise. A distinct advantage of this topology is its tolerance to input parasitic capacitance which can be used to provide good electro-static discharge (ESD) protection without sacrificing its noise performance and power consumption. A compact 3.1\u250010.6 GHz WDA IC is built on a 130 nm CMOS process. Experimental results show 2.3\u25004.5 dB NF at 23 mW power consumption.
\r\n\r\nUsing concurrency in wireless link can boost communication data rate. As a proof-of concept, we propose dynamically scalable concurrent communication by dividing the 7.5 GHz bandwidth of the unlicensed 3.1\u250010.6 GHz spectrum into seven concurrent channels. A CMOS octa-core RF receiver is implemented to validate the idea. Based on the receiver measurement results, a wireless link can be built to achieve a 16 Gbps channel limit at five meter TX-RX distance at 400 mW power consumption.
\r\n\r\nTunable concurrency can improve the receiver diversity. A prototype 6\u250018 GHz concurrent tunable dual-band phased array receiver element IC is proposed and built on a 130 nm CMOS process. Experimental results demonstrate successful dual-band RF reception within a low band (6\u250010.4 GHz) and high band (10.4\u250018 GHz) with 300 MHz baseband bandwidth. A final four-element phased array receiver built from the prototyped ICs shows an array pattern with worst-case 21 dB peak-to-null ratio across all frequencies.
\r\n\r\nConcurrency can also be used to achieve multi-beam reception by providing multiple phase-shifts for each RF signals and combining them separately at baseband outputs. A 10.4\u250018 GHz concurrent dual-beam phased array receiver is proposed based on this concept, and is implemented on a 130 nm CMOS process. A final four-element phased array system shows successful concurrent dual-beam reception at the same RF frequency.
Yu-Jiu Wang (209\r\n", "doi": "10.7907/FZ1R-MJ30", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:3312", "collection": "thesis", "collection_id": "3312", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09022008-113511", "primary_object_url": { "basename": "Thesis_PJChen_2008.pdf", "content": "final", "filesize": 15588540, "license": "other", "mime_type": "application/pdf", "url": "/3312/1/Thesis_PJChen_2008.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Implantable Wireless Intraocular Pressure Sensors", "author": [ { "family_name": "Chen", "given_name": "Po-Jui", "clpid": "Chen-Po-Jui" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Meng", "given_name": "Ellis", "clpid": "Meng E-F-C" }, { "family_name": "Burdick", "given_name": "Joel Wakeman", "clpid": "Burdick-J-W" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The work in this thesis aims to develop a suite of biomedical microdevice implants, with an intense focus on pressure sensors, for glaucoma study and management featuring the enabling micro-electro-mechanical-system (MEMS) technologies and the use of parylene (poly-para-xylene) as a biocompatible MEMS material. The problems of the debilitating eye disease glaucoma threaten tens of millions of people worldwide with loss of vision, and are not completely resolved using the current non-optimal clinical procedures. Given the relation of neuropathy and the physiological parameter of intraocular pressure (IOP) in glaucoma from clinical findings, such parylene-based MEMS implants are investigated to realize physical IOP monitoring and regulation, and further to accomplish continuous, direct, accurate, reliable, and more effective glaucoma detection and treatment.
\r\n \r\nMiniaturized parylene-based passive pressure sensors are presented in this thesis for IOP monitoring. Complete design, fabrication, characterization, and analysis of such MEMS implants are described to demonstrate their feasibility, covering both engineering and surgical/biological aspects of the proposed applications. Their passive behaviors, based on the comprised micromechanical structures, facilitate unpowered device operations. In addition, such devices are microfabricated in suitable form factors so that minimally invasive suture-less implantation procedures are possible, minimizing time and complexity of the surgeries. Two types of micromachined wireless pressure sensors are developed utilizing optical and electrical sensing methodologies, respectively, to explore the possibility of the proposed implant approach. On-bench experimental results verify that wireless pressure sensing with 1 mmHg accuracy in the 0\u2013100 mmHg range can be achieved using both types of devices. Surgical studies, including ex vivo and in vivo animal tests, confirm the bioefficacy and biostability of the device implants in the intraocular environment. With the attempt of providing implementation concepts of the MEMS implant approaches for ultimate glaucoma study and management in practice, system-level designs and configurations involving such microdevice implants are briefly described as well. Micromachined passive-valved flow-control devices with designed surgical and engineering features are also developed (experimentally achieving 0\u2013100 mmHg and 0\u201310 uL/min pressure and flow rate regulation ranges) to investigate the feasibility and possibility of such implant approach for unpowered physical IOP regulation in glaucoma treatment.
\r\n", "doi": "10.7907/46T7-0P24", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:1684", "collection": "thesis", "collection_id": "1684", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05082009-143935", "primary_object_url": { "basename": "Thesis_Motofumi_Arii.pdf", "content": "final", "filesize": 10337702, "license": "other", "mime_type": "application/pdf", "url": "/1684/1/Thesis_Motofumi_Arii.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Retrieval of Soil Moisture under Vegetation Using Polarimetric Radar", "author": [ { "family_name": "Arii", "given_name": "Motofumi", "orcid": "0000-0002-3242-7987", "clpid": "Arii-Motofumi" } ], "thesis_advisor": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "van Zyl", "given_name": "Jakob J.", "clpid": "van-Zyl-J-J" }, { "family_name": "Kim", "given_name": "Yunjin", "clpid": "Kim-Yunjin" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Elachi", "given_name": "Charles", "clpid": "Elachi-C" }, { "family_name": "van Zyl", "given_name": "Jakob J.", "clpid": "van-Zyl-J-J" }, { "family_name": "Kim", "given_name": "Yunjin", "clpid": "Kim-Yunjin" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The unique contributions of this thesis are: 1) a polarimetric classification algorithm that is a significant improvement over an existing algorithm and 2) introduction of a cube technique to retrieve soil moisture under vegetation.
\r\n\r\nThe most widely used classification algorithm is the three-component scattering technique. Even though it includes three dominant scattering mechanisms, the decomposition approach can cause a non-physical solution due to incorrect assumptions. The Adaptive Non Negative Eigenvalue Decomposition approach in this thesis produces correct solution. It appears that this new approach provides better classification results. It is a significant improvement over the existing technique.
\r\n\r\nA cube technique is introduced to retrieve soil moisture under vegetation. Using this approach, we have evaluated the retrieval accuracy of several polarimetric combinations. The effects of the incorrect vegetation model and data noise were investigated. In addition, the proposed cube algorithm can be improved by applying the classification result.
\r\n", "doi": "10.7907/SKJ9-KT40", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:2531", "collection": "thesis", "collection_id": "2531", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06092009-113849", "primary_object_url": { "basename": "Bardin_thesis_final.PDF", "content": "final", "filesize": 7572900, "license": "other", "mime_type": "application/pdf", "url": "/2531/1/Bardin_thesis_final.PDF", "version": "v2.0.0" }, "type": "thesis", "title": "Silicon-Germanium Heterojunction Bipolar Transistors for Extremely Low-Noise Applications", "author": [ { "family_name": "Bardin", "given_name": "Joseph Cheney", "orcid": "0000-0002-6523-6730", "clpid": "Bardin-Joseph-Cheney" } ], "thesis_advisor": [ { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "thesis_committee": [ { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Zmuidzinas", "given_name": "Jonas", "clpid": "Zmuidzinas-J" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Historically speaking, the world of extremely low-noise solid-state amplification has been dominated by exotic technologies such as InP and GaAs HEMTs. By cryogenically cooling these devices, it is possible to realize microwave amplifiers with noise temperatures as low as 5K over decades of bandwidth. Although HEMTs can provide very low noise amplification when cooled to cryogenic temperatures, their radiometer performance is limited by intrinsic transconductance fluctuations. It is believed that bipolar devices do not suffer from this problem. As industry has invested more and more money into silicon based technologies, silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) have continued to improve and are now at the point where they are beginning to become competitive with InP HEMTs for microwave cryogenic low-noise amplifiers. Although extremely high frequency device operation has been observed at cryogenic temperatures, little work has been done on modeling the noise of cooled SiGe HBTs.
\r\n\r\nIn this report, a thorough investigation into the theoretical and practical aspects of using silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) for extremely low-noise applications is presented. The dissertation is broken up into three sections:
\r\n\r\n1) Background information: The fundamentals of SiGe HBTs are presented along with a discussion of how the properties of semiconductors change at cryogenic temperatures, as well the impact that these changes have on the performance of the devices.
\r\n\r\n2) Modeling: A comprehensive study of seven state-of-the-art HBTs at temperatures ranging from 18 K to 300 K is presented. The devices are compared in terms of dc, small-signal, and noise performance, and small-signal noise models are extracted. The section concludes with a brief summary of the important conclusions regarding the performance of SiGe devices at cryogenic temperatures.
\r\n\r\n3) Applications: The models developed previously are applied to the design of several state-of-the-art LNAs in both MMIC and discrete form. Noise performance better than 2 K is achieved in the low-GHz range, which is comparable to the best InP results. The section concludes with a discussion of some high-impedance differential amplifiers which have recently been fabricated.
\r\n", "doi": "10.7907/MCPE-4M30", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:1073", "collection": "thesis", "collection_id": "1073", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-03232009-014403", "primary_object_url": { "basename": "dissertation_wangg.pdf", "content": "final", "filesize": 5849141, "license": "other", "mime_type": "application/pdf", "url": "/1073/1/dissertation_wangg.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Compact Nonlinear Optical Devices in Silicon-Polymer Hybrid Material System", "author": [ { "family_name": "Wang", "given_name": "Guangxi", "clpid": "Wang-Guangxi" } ], "thesis_advisor": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" } ], "thesis_committee": [ { "family_name": "Scherer", "given_name": "Axel", "clpid": "Scherer-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" }, { "family_name": "Inoue", "given_name": "Yoku", "clpid": "Inoue-Yoku" }, { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Recently, integrated silicon photonics has become a topic of rising interests, due to its great potential to induce significant improvements in modern communication and computation systems. While optics is often viewed as a favorable solution to many issues faced by the rapidly evolving microelectronic technology, the high cost, large physical size, and discrete configuration of conventional optics have largely restricted its applications. The introduction of silicon nanophotonics permits a new look at the idea of incorporating optics with traditional electronic integrated circuits in a sensible and feasible fashion.
\r\n\r\nIn this dissertation, emphasis is placed on investigating nonlinear devices built in silicon but complemented by nonlinear polymer materials. Basic optical guiding and coupling components for silicon on insulator platform are first discussed, followed by a detailed description of the design, fabrication, and testing procedures of a Pockels effect electro-optic modulator based on nonlinear polymer-coated silicon nanostructures. Discussion is further expanded on other related devices that also make use of the second-order nonlinear effect, and designs to improve the speed and efficiency of existing devices are also elaborated. Finally, a third-order nonlinear all-optical modulation device is presented with a series of carefully designed experiments to verify its ultrafast operation.
\r\n", "doi": "10.7907/VJX4-5T05", "publication_date": "2009", "thesis_type": "phd", "thesis_year": "2009" }, { "id": "thesis:1879", "collection": "thesis", "collection_id": "1879", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-05192008-132422", "primary_object_url": { "basename": "Thesis.pdf", "content": "final", "filesize": 9566604, "license": "other", "mime_type": "application/pdf", "url": "/1879/1/Thesis.pdf", "version": "v2.0.0" }, "type": "thesis", "title": "Microfabricated High-Performance Liquid Chromatography (HPLC) System with Closed-Loop Flow Control", "author": [ { "family_name": "Shih", "given_name": "Jason J.", "clpid": "Shih-Jason-J" } ], "thesis_advisor": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" } ], "thesis_committee": [ { "family_name": "Tai", "given_name": "Yu-Chong", "clpid": "Tai-Yu-Chong" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Yang", "given_name": "Changhuei", "clpid": "Yang-Changhuei" }, { "family_name": "Vaidyanathan", "given_name": "P. P.", "clpid": "Vaidyanathan-P-P" }, { "family_name": "Lee", "given_name": "Terry D.", "clpid": "Lee-T-D" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "This thesis presents the development of a microfabricated high-performance liquid chromatography (HPLC) system. The design, fabrication, and characterization of individual HPLC components such as high-pressure pumps, mixers, flow sensors, composition sensors, separation columns, filters, and detectors is presented. These individual components were then integrated to create robust, feedback-driven separation systems capable of performing gradient, reverse-phase, nanoscale HPLC. Two separate separation systems were created. The first integrated system was a microfluidic device for HPLC tandem mass spectrometry (HPLC-MS/MS) designed for proteomic applications. The second system was a portable HPLC conductivity detection (HPLC-CD) system designed for point-of-care applications such as biodetection. Both systems demonstrated good performance and repeatability. The performance of these systems is largely attributable to the development of HPLC-compatible sensors that could provide precise control over the elution profiles. These microfluidic closed-loop flow control systems represent an important advancement in the microfluidics field, where open-loop flow control is universally used, and risks becoming inadequate with the increasing complexity of microfluidic systems.", "doi": "10.7907/8A6W-2X34", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:5057", "collection": "thesis", "collection_id": "5057", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-12182007-163333", "primary_object_url": { "basename": "Thesis_v2_combined_new_v2.pdf", "content": "final", "filesize": 4563403, "license": "other", "mime_type": "application/pdf", "url": "/5057/1/Thesis_v2_combined_new_v2.pdf", "version": "v3.0.0" }, "type": "thesis", "title": "Optofluidic Microscopy: Technology Development and Its Applications in Biology", "author": [ { "family_name": "Heng", "given_name": "Xin", "clpid": "Heng-Xin" } ], "thesis_advisor": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" } ], "thesis_committee": [ { "family_name": "Yang", "given_name": "Changhuei", "orcid": "0000-0001-8791-0354", "clpid": "Yang-Changhuei" }, { "family_name": "Psaltis", "given_name": "Demetri", "orcid": "0000-0003-4684-8800", "clpid": "Psaltis-D" }, { "family_name": "Emami", "given_name": "Azita", "orcid": "0000-0002-6945-9958", "clpid": "Emami-A" }, { "family_name": "Sternberg", "given_name": "Paul W.", "orcid": "0000-0002-7699-0173", "clpid": "Sternberg-P-W" }, { "family_name": "Troian", "given_name": "Sandra M.", "orcid": "0000-0003-1224-6377", "clpid": "Troian-S-M" }, { "family_name": "Tai", "given_name": "Yu-Chong", "orcid": "0000-0001-8529-106X", "clpid": "Tai-Yu-Chong" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "The Optofluidic Microscope (OFM) is a new imaging platform based upon nanoapertures that are fabricated on planar metallic film, whilst microfluidic delivery technology is used to transport the objects-of-interest. The planar nature of OFM makes it ideal to integrate with other micro total analysis systems, such as cell sorters or cell culturing chambers. Furthermore, a variety of imaging functionalities, such as differential phase contrast, fluorescence, and Raman spectroscopy can potentially fit into a single OFM device.
\r\n\r\nThis thesis reports on the early technology development of Optofluidic Microscopy. I have built a variety of off-chip prototypes of OFM that all possess different functionalities. These OFM prototypes include 1D array OFM, hydraulically pumped OFM, 2D nanoaperture grid OFM, super high-resolution OFM, OFM coupled with optical tweezer actuation, fluorescent OFM, electrokinetic enabled OFM, etc.
\r\n\r\nI applied the first OFM prototype in imaging Caenorhabditis elegans (C. elegans) larvae and characterizing different genotypes. Later on, the microscopy properties of OFM, such as the optical resolution and the depth of field, were thoroughly investigated both experimentally and theoretically. More recently, I successfully combined optical tweezers with a grid-based OFM prototype, which was then used in high-resolution imaging of microspheres and a few biological samples. In addition, preliminary results on fluorescence OFM imaging were also demonstrated.
\r\n\r\nI trust that these functionalities, after being demonstrated off-chip, can be readily fabricated and then assembled as a complete on-chip OFM. It will eventually enable a real \"microscale microscope on a chip\".
\r\n", "doi": "10.7907/JAYF-RX26", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" }, { "id": "thesis:5227", "collection": "thesis", "collection_id": "5227", "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-06082008-174204", "primary_object_url": { "basename": "AydinBabakhaniThesis.pdf", "content": "final", "filesize": 7140526, "license": "other", "mime_type": "application/pdf", "url": "/5227/1/AydinBabakhaniThesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Direct Antenna Modulation (DAM) for On-Chip mm-Wave Transceivers", "author": [ { "family_name": "Babakhani", "given_name": "Aydin", "orcid": "0000-0001-8123-9061", "clpid": "Babakhani-Aydin" } ], "thesis_advisor": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" } ], "thesis_committee": [ { "family_name": "Hajimiri", "given_name": "Ali", "clpid": "Hajimiri-A" }, { "family_name": "Emami", "given_name": "Azita", "clpid": "Emami-A" }, { "family_name": "Hassibi", "given_name": "Babak", "clpid": "Hassibi-B" }, { "family_name": "Rutledge", "given_name": "David B.", "clpid": "Rutledge-D-B" }, { "family_name": "Weinreb", "given_name": "Sander", "clpid": "Weinreb-S" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "In the last few decades the puissant desire to miniaturize the digital circuits to achieve higher speed and larger density has shaped the evolution of the silicon-based technologies. This development opens a new era in the field of millimeter-wave electronics in which many low-cost high-yield silicon-based transistors can be used on a single chip to enable creation of novel architectures with unique properties not achievable with old processes. In addition to this high level of integration capability, the die size of comparable or even larger than the wave-length makes it possible to integrate antennas, transceivers, and digital circuitry all on a single silicon die.
\r\n\r\nIt is important to realize that although smaller parasitic capacitors and shorter transistor channels have improved fT and fmax of transistors, extremely thin metal layers, highly doped substrates, and low breakdown voltage transistors have severely affected the performance of analog and RF building blocks. For example, thin metal layers have increased the loss and lowered the quality factor of the building blocks such as capacitors and inductors and low breakdown voltage transistors have made the power generation quite challenging. Additionally, if not carefully designed, small wave-lengths in the millimeter-wave range may cause unintended radiation by on-chip components. In this dissertation, we address these issues in design of millimeter-wave silicon-based single-chip phased-array transceivers with integrated antennas. We also introduce the technique of Direct Antenna Modulation (DAM) and implement two proof-of-concept chips operating at 60 GHz.
\r\n\r\nWe will present the receiver and the on-chip antenna sections of a fully integrated 77 GHz four-element phased-array transceiver with on-chip antennas in silicon. The receiver section of the chip includes the complete down-conversion path comprising low-noise amplifier (LNA), frequency synthesizer, phase rotators, combining amplifiers, and on-chip dipole antennas. The signal combining is performed using a novel distributed active combining amplifier at an IF of 26 GHz. In the LO path, the output of the 52 GHz VCO is routed to different elements and can be phase shifted locally by the phase rotators. A silicon lens on the backside is used to reduce the loss due to the surface-wave power of the silicon substrate. Our measurements show a single-element LNA gain of 23 dB and a noise figure of 6.0 dB. Each of the four receive paths has a gain of 37 dB and a noise figure of 8.0 dB. Each on-chip antenna has a gain of +8 dBi.
\r\n\r\nA direct antenna modulation (DAM) technique is also introduced, where the radiated far-field signal is modulated by time-varying changes in the antenna near-field electromagnetic (EM) boundary conditions. This enables the transmitter to send data in a direction-dependent fashion producing a secure communication link. The transmitter architecture makes it possible to use narrow-band highly-efficient switching power amplifiers to transmit wideband constant and non-constant envelope modulated signals. Theoretically, these systems are capable of transmitting independent data in multiple directions at full-rate concurrently using a single transmitter. Direct antenna modulation (DAM) can be performed by using either switches or varactors. Two proof-of-concept DAM transmitters operating at 60GHz using switches and varactors are demonstrated in silicon proving the feasibility of this approach.
", "doi": "10.7907/BS6T-1S20", "publication_date": "2008", "thesis_type": "phd", "thesis_year": "2008" } ]