The optimization of drive and sense circuit in silicon micro-machined resonant accelerometer

Abstract

In silicon micro-machined resonant accelerometer, a drive and sense circuit based on ring diode is used, since the comb capacitance of the resonator is small and its working frequency is above 10 kHz. But there still exist some problems, such as serious delay and small detection sensitivity. To improve these problems, theoretical derivation and calculation of the sense circuit under static and dynamic situation are carried on, and a simulation circuit in Multisim is built by using the voltage-controlled capacitor instead of the comb capacitor after joining the drive circuit. According to the simulation results, the actual circuit parameters are optimized, which reduces the delay from 10 µs to 0.2 µs and improves the detection sensitivity to 41.3 V/pF. Finally the measurement noise of capacitance detection is below 0.5 aF/√Hz, equivalent to a displacement detection noise of 48 pm/√Hz. The improvement of signal-to-noise ratio allows a lower vibration amplitude of the resonator to obtain lower acceleration measurement noise.