Advanced single-chip temperature stabilization system for silicon MEMS resonators and gyroscopes
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The main objective of this research is to develop temperature and frequency stabilization techniques for silicon MEMS oven-controlled crystal oscillators (MEMS OCXO) with high-frequency stability. The device was built upon an ovenized platform that used a micro-heater to adjust the temperature of the resonator. Structural resistance-based (Rstruc) temperature sensing was used to improve the self-temperature monitoring accuracy of the silicon MEMS resonator. An analog feedback micro-oven control loop and a feedforward digital calibration scheme were developed for a 77MHz MEMS oscillator, which achieved a ±0.3ppm frequency stability from -25°C to 85°C. An AC heating scheme was also developed to enable tighter integration of the resonator, temperature sensor (Rstruc) and heaters. This temperature stabilization technique was also applied to silicon MEMS mode-matched vibratory x/y-axis and z-axis gyroscopes on a single chip. The temperature-induced frequency change, scale factor and output bias variations were all reduced significantly. The complete interface circuit for the single-chip three axes gyroscopes were also developed with an innovative trans-impedance amplifier to reduce the input-referred noise. For the first time, the simultaneous operation of mode-matched vibratory 3-axis MEMS gyroscopes on a single chip was demonstrated.