Low-Noise Quality Factor Tuning in Nondegenerate MEMS Gyroscope Without Dedicated Tuning Electrode

Abstract

Quality factor tuning is attractive in degenerate (DE) and nondegenerate (NDE) MEMS gyros for drift suppression or shock and vibration immunity. This paper proposes three resistance-based Q-factor tuning approaches without dedicated electrodes for NDE gyro. The inherent sensing capacitance is utilized as a Q-tuning mechanism for low C-SWaP (cost, size, weight, and power). Routing traces on MEMS or ASIC chips as well as the input impedance of charge-sensitive-amplifier (CSA) are utilized as damping sources, respectively. The theoretical and experimental results indicate Q-tuning utilizing the CSA's input impedance doesn't deteriorate the gyro's noise floor (ARW = 0.01°/√h, BI = 0.12°/h). Large-scale Q-tuning using the regulation of polarization voltage reduces the sensing Q-factor from 38k to 3k. The gyro's settling time after shock is also reduced from 1.4s to 0.13s after Q-tuning. Besides, a frequency-independent fine Q-tuning using tail current regulation in Opam is proposed to correct the thermal variation of the sensing Q-factor. It improves the gyro's bias drift from 1.5°/s to 0.2°/s. This work presents a low C-SWaP Q-tuning solution for high-end industrial MEMS gyro.