Two new power conversion techniques, the constant-frequency zero-voltage-switching multiresonant-converter (CF ZVS-MRC) technique and the zero-voltage-switching technique that uses the magnetizing inductance of the power transformer as a resonant element {ZVS {L_M)) are proposed. analyzed, and evaluated for high-frequency applications. In addition, a novel design optimization approach for resonant type converters is introduced. Complete dc analysis of CF forward and half-bridge {HB) ZVS-MRCs are given, and the dc voltage-conversion-ratio characteristics for each of these two converters are derived. Graphic design procedures that maximize the efficiency and minimize current and voltage stresses are established. The design guidelines are verified on a 50 W CF forward ZVS-MRC operating with a switching frequency above 2 MHz, and on a 100 W HB ZVS-MRc operating with a switching frequency of 750 kHz. The ZVS (LM) technique is developed to eliminate the need for a large, inefficient external resonant inductor in ZVS resonant converters. This new family of isolated converters can operate with zero-voltage-switching of the primary active switches only (quasi-resonant (QR) operation) or with soft-switching of all semiconductor devices (multi-resonant (MR) operation). Furthermore, variable and constant frequency operation of all topologies in this new family of dc/dc converters are possible. A complete dc analysis of the HB ZVS-MRC (L_M) is given, and the dc voltage-conversion-ratio characteristics are derived. Design guidelines are defined using the same graphic method employed in the design of CF ZVS-MRCs. Constant frequency implementation of the HB ZVS-MRC (L_M) using controllable saturable inductors is also proposed. Finally, a novel approach to evaluate and design resonant converters based on the minimization of reactive power is developed. / Ph. D.

An investigation into the responses of microbeams to electric actuations is presented. Attention is focused mainly on the use of microbeams in two important MEMS-based devices: capacitive microswitches and resonant microsensors. Nonlinear models are developed to simulate the behavior of the microbeams in each device. The models account for mid-plane stretching, an applied axial load, a DC electrostatic force, and, for the case of resonant sensors, an AC harmonic force. Further, a novel method that uses a reduced-order model is introduced for simulating the behavior of microbeams under a DC electrostatic force. The presented method shows attractive features, like for example, a high stability near the pull-in and a low computational cost. Thus, it can be of significant benefit to the development of MEMS design software. The static behavior of microbeams under electrostatic forces is studied using two methods. One method employs a shooting technique for solving the boundary-value problem that governs the static behavior. The second method is based on solving an algebraic system of equations obtained from the reduced-order model. Further, the eigenvalue problem describing the vibrations of a microbeam around its statically deflected position is solved using a shooting method to obtain the microbeam mode shapes and natural frequencies. The dynamic behavior of resonant microbeams is also investigated. A perturbation method, the method of multiple scales, is used to obtain two first-order nonlinear ordinary-differential equations that describe the amplitude and phase of the response and its stability. The results show that an inaccurate representation of the system nonlinearities may lead to an erroneous prediction of the nonlinear resonance frequency of a microbeam. The case of three-to-one internal resonance between the lowest two modes is treated. Finally, the reduced-order model is used to study the dynamic behavior of the electrostatically actuated microbeams. The proposed models are validated by comparing their results with experimental results available in the literature. / Master of Science

The work described in this dissertation can be divided into two parts. The first part is an investigation of the transient behavior and stability property of a phase conjugate resonator (PCR) below threshold. The second part is an experimental and theoretical study of the PCR's spatiotemporal dynamics above threshold. The time-dependent coupled wave equations for four-wave mixing (FWM) in a photorefractive crystal, with two distinct interaction regions caused by feedback from an ordinary mirror, was used to model the transient dynamics of a PCR below threshold. Analytical expressions of the steady state cavity's fields for the case of nondepleted pumps and an absorption free medium were derived and used to determine the self-oscillation conditions. The solutions, through simple frequency domain transformation techniques, were used to define the PCR's transfer function and analyse its stability. Taking into account pump depletion and medium absorption, the transient buildup and decay times of the cavity's fields as well as the specularly reflected and phase conjugate reflected intensities were numerically calculated as functions of a number of system parameters such as the coupling parameter and the pump and probe ratios. General trends were unveiled and discussed in view of the possible use of the PCR in image storage or processing architectures. Experimental results for the buildup and decay times confirmed qualitatively the predicted behavior. / Ph. D.

This thesis describes a method for using stripline resonators to characterize the electrical properties of materials used in the construction of planar geometry transmission lines and circuits. The method characterizes both dielectric and conductor materials. It can be used to find the relative dielectric constant and to separate the conductor and dielectric losses. The separation of the loss terms is achieved by fitting measurements of stripline losses to a well known model. This model identifies the loss terms separately based on variation of the losses with stripline dimensions. This thesis presents the complete stripline resonator model used. The model has been incorporated into a computer simulation which predicts the resonator response. This simulation is useful in many ways, including the design of various resonators needed in experiments. Also presented are the results of an experiment which demonstrates the feasibility of this method when applied to real samples. These results show that this method works well for low loss materials. Further development may produce 6 model which will allow this method to be used on higher loss materials. A similar theoretical derivation may be used to develop a model for using this method with other transmission line structures such as coaxial lines. This method is advantageous because it does not assume that material properties are independent of frequency and can be designed to produce results at a specific frequency. Stripline resonators are easily manufactured and a network analyzer is the only test equipment required. For these reasons, this method can be used to provide accurate results at a low cost. / Master of Science

Narrowband spectral filters find important applications in optical fiber communication systems, particularly in wavelength demultiplexers and single-frequency semiconductor lasers. Conventional Fabry-Perot resonators provide a narrow spectral width but lack the capability of mode discrimination. A new coupled-waveguide Fabry-Perot resonator made of two parallel waveguides with reflecting mirrors at the ends is proposed for application as narrowband tuned spectral filter in single-mode diode lasers and wavelength demultiplexers. The interference of counter propagating waves from reflection by end mirrors and the coupling of waves between the two parallel guides contribute to the operation of this resonator structure. Thus, the device exhibits the attributes of both Fabry-Perot resonator and directional coupler. The coupled-mode theory of parallel waveguides is employed to analyze the proposed structure. Spectral characteristics are derived from the governing coupled-mode equations and related boundary conditions. Two geometries consisting of identical waveguides, as well as nonidentical waveguides, are examined. The spectral characteristics of the proposed resonator demonstrate that significant improvement in mode discrimination capability and longitudinal mode spacing over the conventional Fabry-Perot resonator is achieved. Numerical results for several example cases are presented and the influence of various parameters on spectral properties are investigated. / Master of Science

This thesis develops a method for obtaining the complex resonant frequency of a post dielectric resonator in the presence of a lossy conductor. A full field analysis is performed on an infinite dielectric rod from which the complex propagation constant and modal solutions are found. Using a single dominant mode (HEM_ll), the boundary conditions at the end of the resonator are enforced, to obtain a complex reflection coefficient. Using the propagation constant from the infinite dielectric rod and the reflection coefficient derived from considering the dielectric-air interface at the resonator ends, a two dimensional search is performed to find the complex frequency for which the gain/phase criterion of the resonator is satisfied. In the final step, boundary conditions are enforced for a lossy conductor at a distance Az from the dielectric which yields the objective -- the complex resonate frequency of a post dielectric in close proximity of a lossy conductor / Master of Science

The rapid development of wireless applications has created a demand for low-cost, compact, low-power hardware solutions. This demand has driven efforts to realize fully integrated, "single-chip" systems. While substantial progress had been made in the integration of many RF and baseband processing elements through the development of new technologies and refinements of existing technologies, progress in the area of fully monolithic filters has been limited due to the losses (low Qs) associated with integrated passive elements in standard IC processes. The work in this thesis focuses on the development low-loss, Q-enhanced LC filters in GaAs E/D-SAGFET technology. This thesis presents a methodology for designing Q-enhanced LC resonators and low-loss, monolithic LC filters based on these resonators. The first phase of this work focused on the Q-enhancement of LC resonator structures using FET-based active negative resistance circuits. Three passive resonators were designed, fabricated, and measured to determine their loss and frequency response. Furthermore, six Q-enhanced resonators were designed, fabricated, and measured to compare the performance of various negative resistance circuit designs. In the second phase of this work, four of these Q-enhanced resonator designs were used to implement fully-integrated second-order Butterworth bandpass filters. Each filter was designed for a 60 MHz, -3 dB bandwidth centered at 1.88 GHz, corresponding to the North American PCS transmit band. The best filter design achieves 0 dB of passband insertion loss while consuming 16 mA of current from a 3 V source (48 mW). Passband gain (up to 15 dB) can be achieved with increased bias current before instability is encountered. The filter provides more than 30 dB of rejection at 1.7 and 2 GHz and more than 70 dB of rejection below 1.5 GHz. In the filter passband, the noise figure is 12 dB and the output 1 dB compression point is -18 dBm. These Q-enhanced LC filters have potential application as image-reject filters in GaAs integrated transceiver designs. / Master of Science

No description available.

This dissertation reports very novel solutions for the trimming and compensation of various parameters of silicon micromechanical resonators and resonator-arrays. Post-fabrication trimming of resonance frequency to a target value is facilitated by diffusing in a deposited thin metal layer into a Joule-heated silicon resonator. Up to ~400 kHz of trimming-up and trimming-down in a 100 MHz Silicon Bulk Acoustic Resonators (SiBARs) are demonstrated via gold and aluminum diffusion respectively. The dependence of the trimming range on the duration of Joule heating and value of current passed are presented and the possibility of extending the trimming range up to ~4 MHz is demonstrated. Passive temperature compensation techniques are developed to drastically reduce the temperature coefficient of frequency (TCF) of silicon resonators. The dependence of TCF on the charge carriers in silicon are extensively studied and exploited for the very first time to achieve temperature compensation. A charge surplus via degenerate doping using boron and aluminum is shown to reduce a starting TCF of -30 ppm/°C to -1.5 ppm/°C while a charge depletion effected by creating multiple pn-junctions reduces the TCF to -3 ppm/°C. Further, shear acoustic waves in silicon microresonators have also been identified to effect a TCF reduction and have been excited in a concave SiBAR (or CBAR) to exhibit a TCF that is 15 ppm/°C lesser than that of a conventional rectangular SiBAR. The study on quality factor (Q) sensitivity to the various crystallographic axis of transduction in silicon resonators show that the non-repeatability of Q across various fabrication batches are due to the minor angular misalignment of ≤ 0.5° during the photolithography processes. Preferred axes of transduction for minimal misalignment sensitivity are identified and novel low-loss resonator-array type performances are also reported from a single resonator while transduced along certain specific crystallographic axes. Details are presented on an unprecedented new technique to create and fill charge traps on the silicon resonator which allows the operation of the capacitive SiBARs without the application of any polarization voltages (Vp) for the first time, making them very attractive candidates for ultra-low-power oscillator and sensor applications. Finally, a fabrication process that integrates both the capacitive and piezoelectric actuation/sensing schemes in microresonators is developed and is shown to compensate for the parasitics in capacitive silicon resonators while maintaining their high-Q.

Optical traveling-wave resonator architectures have shown promise for the realization of many compact photonic functionalities in different research disciplines. Realizing these resonator structures in high-index contrast silicon enables dense and large scale integration of large arrays of functionalized resonators in a CMOS-compatible technology platform. Based on these motivations, the main focus of this Ph.D. research has been on the device physics, modeling, implementations, and applications of planar ultra-high Q silicon traveling-wave microresonators in a silicon-on-insulator (SOI) platform. Microdisk, microring, and racetrack resonators are the three general traveling-wave resonator architectures of interests that I have investigated in this thesis, with greater emphasis on microdisks. I have developed efficient tools for the accurate modeling of these resonators. The coupling to these resonators has been through a nano-waveguide side coupled to them. For this purpose, I have developed a systematic method for engineering a waveguide-resonator structure for optimum coupling. I have addressed the development of nanofabrication techniques for these resonators with efficient interaction with a nano-waveguide and fully compatible with active electronic integration. The outcome of the theoretical design, fabrication, and characterization of these resonators is a world-record ultra-high Q (3×10[superscript 6]) with optimum waveguide-resonator interaction. I have investigated the scaling of these resonators toward the ultimate miniaturization and its impact on different physical properties of the resonators. As a result of these investigations, I have demonstrated miniaturized Si microdisk resonators with radii of ~ 1.5 micron and Q > 10⁵ with single-mode operation over the entire large free-spectral range. This is the highest Q (~ one order more than that in previously reported data) that has been obtained for a Si microdisk resonator with this size on a SiO₂ substrate. I have employed these resonators for more advanced functionalities such as large-scale integration of resonators for spectroscopic and filtering applications, as well as the design of flat-band coupled-resonator filter structures. By proposing a systematic method of design, I have shown ultra-compact coupled-resonator filters with bandwidths ranging from 0.4 to 1 nm. I have theoretically and experimentally investigated the performance of ultra-high Q resonators at high powers and in the presence of nonlinearities. At high powers, the presence of two-photon absorption, free-carrier generation, and thermo-optic properties of silicon results in a rich dynamic in the response of the resonator. In both theory and experiment, I have predicted and demonstrated self-sustained GHz oscillation on the amplitude of an ultra-high Q resonator pumped with a continuous-wave laser.