The mammalian cochlea has been the inspiration to develope contemporary cochlear implants and active dynamic sensors that operate in the sensor's resonance region and possess favorable nonlinear characteristics. In the present work, multi-channel and self-sensing active artificial hair cells (AHCs) made of piezoelectric cantilevers and controlled by a cubic damping feedback controller are developed numerically and experimentally. These novel AHCs function near a Hopf bifurcation and amplify or compress the output by a one-third power-law relationship with the input, analogous to the mammalian cochlear amplifier. The multi-channel AHCs have extended frequency bandwidth to sense over multiple resonant frequencies, unlike conventional single-channel AHCs. Therefore, the adoption of these AHCs reduces the number of required sensors to cover the desired bandwidth of interest in an array format. Furthermore, a novel self-sensing active AHC is created in this study using quadmorph beams for future cochlear implants or sensor design applications. The self-sensing scheme allows miniaturization of the system, embedding AHCs in a limited space, and fabrication of AHC arrays by omitting external sensors from the system for practical implementation. Preliminary research on the extension of this research to MEMS AHCs and arrays of AHCs is also presented. The active AHCs can lead to transformative improvements in the dynamic range, sharpness of the response, and threshold of sound detection in cochlear implants to aid individuals with sensorineural hearing loss. Additionally, they can enhance the dynamic properties of sensors such as fluid flow sensors, microphones, and vibration sensors for various applications. / Doctor of Philosophy / In the mammalian auditory system, the acoustic wave that enters the ear canal is transmitted to the cochlea of the inner ear where it is decomposed into its frequency components. The cochlea then amplifies faint sounds and compresses high-level signals and as these processes stop due to damage, severe hearing loss occurs. Therefore, the present work is focused on developing artificial hair cells (AHCs) that can accurately replicate cochlea's behavior and aid the creation of prostheses for hearing restoration. In this work, the AHC is a beam with piezoelectric layers that is integrated with a control system designed to apply the cochlea-like amplification/compression on the beam. Experimental and simulation results show that the AHC is able to amplify or compress the output based on its input level similar to the mammalian cochlea. In contrast to previous designs of AHCs where each AHC could sense a single frequency, the system developed in this work possesses multiple sensing channels to increase the frequency range of the AHC. Furthermore, the development of a novel self-sensing scheme allows the omission of the external sensor that was required for the AHC operation in previous devices. This advancement in the self-sensing AHC design paves the way for creating fully implantable AHCs to replace the damaged parts of the cochlea. These multi-channel self-sensing AHCs have the potential to be used in the creation of cochlear implants, or sensors such as accelerometers, microphones, and hydrophones with improved dynamic properties. AHCs with different lengths, i.e. different sensing frequencies, can be mounted in an array format to cover the speech frequency range for speech recognition in individuals with hearing loss.

As the oil industry continues to drill deeper to reach previously untapped wells, the operating environments for electronic systems become harsher, especially due to high temperatures. It is essential to design electronic circuits and systems to be able to withstand these extreme temperatures. The proposed power amplifier (PA) has been designed for a downhole communication system operating at an ambient temperature of 230oC. GaN technology was chosen primarily due to its ability to function at a high junction temperature. The proposed PA was designed with Qorvo's T2G6003028-FL HEMT as it operates reliably at a high junction temperature (T_J) and also the package offers low junction to case thermal resistance . The proposed PA can operate reliably up to an ambient temperature of 230oC using passive cooling opposed to active cooling. At 230 C it operates in class A with a peak PAE of 25.03%, maximum output power of 1.66 W, peak gain of 24.5 dB, center frequency of 255 MHz with 1dB ripple in the passband over a 60 MHz bandwidth, 1dB output compression of approximately 32 dBm, and OIP3 of 37.9dBm. CW measurements were taken for all parameters. / Master of Science

As the oil industry continues to drill deeper to reach new wells, electronics are being required to operate at extreme pressures and temperatures. Coupled with substantial real-time data targets, the need for robust high speed electronics is quickly on the rise. This paper presents a high temperature wideband low noise amplifier (LNA) with zero temperature coefficient maximum available gain (ZTCMAG) biasing for a downhole communication system. The proposed LNA is designed and prototyped using 0.25μm GaN on SiC RF transistor technology, which is chosen due to the high junction temperature capability. Measurements show that the proposed LNA can operate reliably up to an ambient temperature of 230°C with a minimum noise figure (NF) of 2.0 dB, gain of 16.1 dB, and P1dB of 19.1 dBm from 230.5MHz — 285.5MHz. The maximum variation with temperature from 25°C to 230°C is 1.53dB for NF and 0.65dB for gain. / Master of Science

Ever since the FCC allocated 7.5 GHz (from 3.1 GHz to 10.6 GHz) for ultra wideband (UWB) technology, interest has been renewed in both academic and industrial circles to exploit this vast spectrum for short range, high data rate wireless applications. The great potential of UWB lies in the fact that it can co-exist with the already licensed spectrum users and can still pave the way for a wide range of applications. However, this wide bandwidth complicates the circuit level implementation of key RF blocks like the power amplifier (PA), transmit/receive switch, low noise amplifier (LNA) and mixers in an UWB transceiver. Though expensive technologies like SiGe or GaAs have been used for transceiver realizations, the ultimate goal is to have a single-chip, low-cost solution which can only be achieved by using CMOS technology. Nevertheless, some of the inherent limitations of CMOS like lower fT of transistors make the design of UWB circuits in CMOS an extremely challenging task. Two proposals- Multi-Band OFDM and Direct-Sequence CDMA have been put before the IEEE 802.15.3a task group to decide on the industry standard for the commercial deployment of this technology. Though the debate on which standard is better has not been resolved, proponents of both the groups have already begun to develop prototypes of their respective proposals. This thesis describes the design of a key RF block in the UWB transceiver - the Power Amplifier. For the first part of this work, a PA suitable for MB-OFDM specifications was designed and fabricated in TSMC 0.18um CMOS technology. The class-AB PA is able to cover the lower UWB frequency band from 3.1 GHz to 4.75 GHz and delivers an output power of -2 dBm at 4 GHz. Simulated results show a gain of 19±2 dB achieved over the entire band and the PA consumes 36.54 mW from a 1.8V supply. In the second part of this work, a PA that meets the DS-CDMA specifications was designed and fabricated. This PA operates in the class-AB regime, delivering an output power of -4.2 dBm with input-1dB compression point at -22 dBm. Complete design and implementation was done using TSMC 0.18um CMOS technology and it consumes a very low power of 25 mW, while realizing a flat gain of 19±1 dB across the whole band of operation. All the above mentioned results are from simulations in SpectreRF and measurements are yet to be taken. Additional features like power ON/OFF scheme and output impedance control has also been incorporated in the design. / Master of Science

As transistor sizes scale down and levels of integration increase, leakage power has become a critical problem in modern low-power microprocessors. This is especially true for ultra-low-voltage (ULV) circuits, where high levels of leakage force designers to chose relatively high threshold voltages, which limits performance. In this thesis, an industry-standard technique known as power-gating is explored, whereby transistors are used to disconnect the power from idle portions of a chip. Present power-gating implementations suffer from limitations including non-zero off-state leakage, which can aggregate to a large amount of wasted energy during long idle periods, and high energy overhead, which limits its use to long-term system-wide sleep modes. As this thesis will show however, by vastly increasing the effectiveness of power-gating through the use of emerging technologies, and by implementing aggressive hardware-oriented power-gating policies, leakage in microprocessors can be eliminated to a large extent. This allows the threshold voltage to be lowered, leading to ULV microprocessors with both low switching energy and high performance. The first emerging technology investigated is the Nanoelectromechnical-Systems (NEMS) switch, which is a CMOS-compatible mechanical relay with near-infinite off-resistance and low on-resistance. When used for power-gating, this switch completely eliminates off-state leakage, yet is compact enough to be contained on die. This has tremendous benefits for applications with long sleep times. For example, a NEMS-power-gated architecture performing an FFT per hour consumes 30 times less power than a transistor-power-gated architecture. Additionally, the low on-resistance can lower power-gating area overhead by 36-83\%. The second technology targets the high energy overhead associated with powering a circuit on and off. This thesis demonstrates that a new logic style specifically designed for ULV operation, Sense Amplifier Pass Transistor Logic (SAPTL), requires power-gates that are 8-10 times smaller, and consumes up to 15 times less boot-up energy, compared to static-CMOS. These abilities enable effective power-gating of an SAPTL circuit, even for very short idle periods. Microprocessor simulations demonstrate that a fine-grained power-gating policy, along with this drastically lower overhead, can result in up to a 44\% drop in energy. Encompassing these investigations is an energy estimation framework built around a cycle-accurate microprocessor simulator, which allows a wide range of circuit and power-gating parameters to be optimized. This framework implements two hardware-based power-gating schedulers that are completely invisible to the OS, and have extremely low hardware overhead, allowing for a large number of power-gated regions. All together, this thesis represents the most complete and forward-looking study on power-gating in the ULV region. The results demonstrate that aggressive power-gating allows designers to leverage the very low switching energy of ULV operation, while achieving performance levels that can greatly expand the capabilities of energy-constrained systems. / Ph. D.

The cochlea is known to exhibit a nonlinear, mechanical amplification which allows the ear to detect faint sounds, improves frequency discrimination, and broadens the range of sound pressure levels that can be detected. In this work, active artificial hair cells (AHC) are proposed and developed which mimic the nonlinear cochlear amplifier. Active AHCs can be used to transduce sound pressures, fluid flow, accelerations, or another form of dynamic input. These nonlinear sensors consist of piezoelectric cantilever beams which utilize various feedback control laws inspired by the living cochlea. A phenomenological control law is first examined which exhibits similar behavior as the living cochlea. Two sets of physiological models are also examined: one set based on outer hair cell somatic motility and the other set inspired by active hair bundle motility. Compared to passive AHCs, simulation and experimental results for active AHCs show an amplified response due to small stimuli, a sharpened resonance peak, and a compressive nonlinearity between response amplitude and input level. These bio-inspired devices could lead to new sensors with lower thresholds of sound or vibration detection, improved frequency sensitivities, and the ability to detect a wider range of input levels. These bio-inspired, active sensors lay the foundation for a new generation of sensors for acoustic, fluid flow, or vibration sensing. / Ph. D.

Millimeter wave (mm-Wave) has become increasingly popular frequency band for next-generation high-speed wireless communications. In mm-Wave, the wireless channel path loss is severe, demanding a high output power in transmitters (Tx) to meet a required SNR in receivers (Rx). Due to the intractable speed-power tradeoff ingrained in silicon processes, however, achieving a high power at mm-Wave, particularly over W-band (> 90 GHz), is challenging in silicon power amplifiers. To relieve the output power burden, phased-arrays are widely adopted in mm-Wave wireless communication systems -- namely, by leveraging a parallel power combining in the space domain, inherent in the phased arrays, the required output power per array element can be reduced significantly with increasing array size. In large arrays ( > 100's -- 1000's number of arrays), the required output power per element could be small, typically around several 10's mW or less in silicon-based phased arrays. In such small-to-medium scale output power level, the static power dissipations by transistor knee voltage and passive components could be a significant portion of the output power, decreasing power efficiency of power amplifiers drastically. This poses a significant concern on the power efficiency of the large-scale silicon-based phased arrays in mm-Wave. Another critical problem in mm-Wave wireless systems design is the increase of passive reactive components loss caused by worsening skin depth effect and increasing dielectric loss through silicon substrate. This essentially degrades the reactive components quality factor (Q) and limits frequency selectivity of the silicon-based mm-Wave systems. This thesis tackles these two major technical challenges to provide high frequency selectivity with maintaining high power efficiency for future mm-Wave wireless systems over W-band and beyond. First, various high-efficiency techniques such as impedance tuning with a reactive component at a cascoding stage in conventional stacked power amplifiers or load-pull based inter-stage matching technique, rather than conventional conjugate matching, have been applied to W-band CMOS and SiGe BiCMOS amplifiers to improve power efficiency with 5-10 dBm output power level, suitable for a large phased array applications, as detailed in Chapter 2 and 3. Second, a 4-tap finite impulse response (FIR) filter based receiver architecture is presented in Chapter 4. The FIR filtered receiver leverages a sinc-pulse type frequency nulls built-in in the transmission-line based FIR filter's frequency response to increase frequency selectivity. The proposed FIR filtered receiver achieves > 40-dB image rejection by placing an image signal at the null frequency at D-band, one of the largest image rejection performance at the highest frequency band reported so far. / Ph. D. / Due to recent advances in Silicon based solid-state technologies, the interest towards the millimeter wave (mm-Wave) frequency band has been emerging for next-generation high-speed wireless communication applications. One of the most significant parameters in a communication system would be the output power of a transmitter. However, the output power is limited especially at mm-wave frequencies. A phased array is one of the viable solutions to overcome this burden by utilizing a parallel power combing in the space domain. The required output power per element can be relieved, typically around several tens of mill watts or less. There are two major factors limiting the output power, which are the high loss of passive and active devices. This dissertation presents solutions to overcome these challenges. In addition, a 4-tap finite impulse response (FIR) filter based receiver architecture is introduced, which rejects unwanted image signals in heterodyne systems by utilizing sinc-pulse type frequency nulls. The proposed FIR filter achieves more than 40 dB of image rejection at D-band (110-170 GHz), which is one of the highest filtering performance in the millimeter-wave frequency band.

There has been increased interest in exploring high frequency (mm-wave) spectrum (particularly the 30 and 60 GHz ranges), and utilizing silicon-based technology for reduced-cost monolithic millimeter integrated circuits (MMIC), for applications such as WLAN, inter-vehicle communication (IVC) automotive radar and local multipoint distribution system (LMDS). Although there has been a significant increase in silicon-based implementations recently, this area still has significant need for research and development. For example, one microwave/mm-wave front-end component that has seen little development in silicon is the power amplifier (PA). Two potential technologies exist for providing a solution for low-cost microwave/mm-wave power amplifiers: 1) Silicon-Germanium (SiGe) HBT and 2) Complementary metal-oxide semiconductor (CMOS). SiGe HBT has become a viable candidate for PA development since it exhibits higher gain and higher breakdown voltage limits compared to CMOS, while remaining compatible with BiCMOS technology. Also, SiGe is potentially lower in cost compared to other compound semiconductor technologies that are currently used in power amplifier design. Hence, this research focuses on design of millimeter-wave power amplifiers in SiGe HBT technology. The work presented in this thesis will focus on design of different power amplifiers for millimeter-wave operating frequencies. Amplifiers present the fundamental trade-off between linearity and efficiency. Applications at frequencies highlighted above tend to be point-to-point, and hence high linearity is required at the cost of lowered efficiency for these power amplifiers. The designed power amplifiers are fully differential topologies based on finite ground coplanar waveguide (FGC) transmission line technology, and have on-chip matching networks and bias circuits. The selection and design of FGC lines is supported through full-wave EM simulations. Tuned single stub matching networks are realized using FGC technology and utilized for input and output matching networks. Two 30-GHz range SiGe HBT PA designs were carried out in Atmel SiGe2RF and IBM BiCMOS 8HP IC technologies. The designs were characterized first by simulations. The performance of the Atmel PA design was characterized using microwave/mm-wave on wafer test measurement setup. The IBM 8HP design is awaiting fabrication. The measured results indicated high linearity, targeted output power range, and expected efficiency performance were achieved. This validates the selection of SiGe HBT as the technology of choice of high frequency point-to-point applications. The results show that it is possible to design power amplifiers that can effectively work at millimeter-wave frequencies at lower cost for applications such as mm-wave WLAN and IVC where linearity is important and required transmitted power is much lower than in cellular handset power amplifiers. Moreover, recommendations are made for future research steps to improve upon the presented designs. / Master of Science

Over the last few decades, the susceptibility of integrated circuits to electrostatic discharge (ESD) induced damages has justified the use of dedicated on-chip protection circuits. Design of robust protection circuits remains a challenging task because ESD failure mechanisms have become more acute as device dimensions continue to shrink. A lack of understanding of the ESD phenomena coupled with the increased sensitivity of smaller devices and time-to-market demands has led to a trial-and-error approach to ESD-protected circuit design. Improved analysis capabilities and a systematic design approach are essential to accomplish the challenging task of providing adequate protection to core circuit(s). The design of ESD protection circuitry for RFIC's has been relatively slow to evolve, compared to their digital counterparts, and is now emerging as a new design challenge in RF and high-speed mixed-signal IC development. Sub-circuits which are not embedded in a single System-on-Chip (SOC), such as RF Power amplifiers (PAs), are of particular concern as they are more susceptible to the various ESD events. This thesis presents the development of integrated ESD protection circuitry for two RFIC Power Amplifier designs. A prototype PA for 2.4 GHz Wireless Local Area Network (WLAN) applications was redesigned to provide protection to the RF input and the PA Control pins. A relatively new technique known as the L-C tank approach was used to protect the RFinput while a standard diode ring approach was used to protect the control line. The protection techniques studied were subsequently extended to a completely protected three-stage PA targeting 1.9 GHz Digitally Enhanced Cordless Telephone (DECT) applications. An on-chip shunt-L-series-C input matching network was used to provide ESD protection to the input pin of the DECT PA. A much more area efficient (as compared to the diode ring technique) Zener diode approach was used to protect the control and signal lines. The PA's RF performance was virtually unaffected by the addition of the protection circuits. Both PAs were designed in a commercially available 0.5 ìm SiGe-HBT process. The partially protected WLAN PA was fabricated and packaged in a 3mm x 3mm Fine Pitch Quad Flat Package FQFP-N 12 Lead package and had a measured ESD protection rating of ± 1kV standard Human Body Model (HBM) ESD test. The simulated DECT PA demonstrated +1.5kV/-4kV HBM performance. / Master of Science

Fiber Raman amplification using the transmission line is a promising technology to increase the repeater distance as well as the capacity of the communication systems. Because of the growing importance of fiber Raman amplification, it is desired to predict the magnitude and shape of the Raman gain spectrum from the doping level and refractive index profiles of different fiber designs. This thesis develops a method to predict the Raman gain coefficients and spectra for a pure silica core fiber and two different types of GeO2-doped silica fibers given their index profiles. An essential feature of the model is the inclusion of the variation in Raman gain coefficient over the mode field due to the variation in the Ge concentration across the fiber core. The calculated Raman gain coefficients were compared with measurements of the peak Raman gain on a step-index GeO2-doped fiber and with published measurements from various sources. Agreement between the calculated and measured peak gain for the step-index fiber was excellent. There was qualitative agreement with published measurements but there were significant differences between the calculated and published gain coefficients, which are not understood. Part of the work sought a way of predicting Raman gain coefficients from a standard gain curve given only the fiber type and the effective area. This approach appears promising for moderately-doped fibers with the proper choice of effective area. / Master of Science