Capacitive Vibration Micromachined Gyroscope Interface Circuit Design, Simulation And Testing

Micromachined vibratory gyroscope has been studied widely and deeply for its unique advantages and broad applications. In this dissertation, we designed, simulated, and tested the interface circuit of the vibratory gyroscope, which is driven by electro- static comb finger forces and detected by capacitance. From the theoretical analysis of the micromachined vibratory gyroscope, we derived its equivalent electrical analogue, which was simulated in PSpice to study the performances of the gyroscope, and obtained its optimized parameters, such as the driving frequency and the voltage for the mode matching. The interface circuit was devided into two parts, one is the driving-circuit and the other is detecting-circuit. Two types of driving-circuit were designed, which are the external applied voltage drive and the self-drive. We simulated the self-drive circuit in PSpice using the equivalent electrical analogue and verified its function. Circuit for detecting the tiny capacitance variation was designed for the detecting-circuit of capacitive micromachined vibratory gyroscope. We proposed the analogue of the gyroscope detecting-capacitance in PSpice, and simulated the detecting-citcuit using the analogue. From the simulation, we optimised the circuit parameters, such as the gain, the filter bandwidth, etc. The system resolution was also obtained from the circuit noise analysis in PSpice. The PCB of the interface circuit was implemented. From the measurement of a micromachined variable capacitor using the interface circuit, we found that the resolution of the circuit was 40 aF.