Design and simulation of micro resonator oscillator for communication circuits

Official URL: http://risc01.sabanciuniv.edu/record=b1083682 (Table of Contents)

In this theses design and simulation of a Micro Electro Mechanical System (MEMS) based oscillator is presented. Electrostatic comb drive is chosen as the core structure in oscillator. MicroElectroMechanical (MEM) vibrating structures such as linear drive resonators can be used as driving components in signal processing applications. The choice of these components is assisted by the fact that these MEM devices display high quality factor values when operated under vacuum. The design of a highly stable oscillator is an example utilizing the linear drive resonators and working samples are demonstrated at 16.5 kHz. For this oscillator to be used in portable communication devices, the operating frequency will have to be increased to at least IF band (> 450kHz). MEMS based microstructures are simulated and prepared for implementation by properly adjusting the physical dimensions of the micromechanical resonator. The Dimensions of the resonator is tuned to achieve higher resonance frequencies. Electrical model and governing equations of interdigitated finger structure are studied. Based on results of these studies a micromechanical oscillator is designed to attain above-mentioned frequency. The study is carried out both analytically and on the equivalent circuit. Integration of MEMS structure with Complementary Metal Oxide Semiconductor (CMOS) electronics is another motivation and driving force of this study. Therefore completely monolithic high-Q micromechanical oscillator integrated with CMOS circuits is aimed and described. As it has high Q (over 80.000) and very stable, laterally driven microresonators can be a good miniaturized replacement of a crystal and surface acoustic wave (SAW) resonator based oscillators used in telecommunication applications. The electrical model of the microresonator is given and used as a frequency selective network in the oscillator design. Different oscillator circuits are designed and simulated to estimate and compare their performance to other mechanical based oscillators (SAW, FBAR, Crystal etc.). Analog CMOS integraated circuits are designed and optimized to achieve highly stable oscillations.