MEMS gyroscope control system using a band-pass continuous-time sigma-delta modulator

This paper presents a MEMS gyroscope control system of using a high-order band-pass continuous-time sigma-delta modulator. Compared with a low-pass discrete-time sigma-delta modulator based solution, the band-pass modulator can considerably decrease the sampling frequency; moreover, the continuous-time architecture has an obvious advantage on PCB prototyping and shorter lead time of the implementation in hardware. System level simulations using MATLAB/Simulink show the proposed sixth order sigma-delta modulator can achieve a high SNR of 100 dB for an angular rate input with an amplitude of 200 degrees/s and a frequency of 32 Hz. A PCB circuit implementation is simulated using Orcad/PSpice to analyze the stability, and implemented in hardware. Measurement of the power spectral density of the output bitstream reveals a noise floor of -90 dBV/Hz(1/2). The prototype is tested on a rate table with an angular rate input, verifying that the principle of the approach of using an electro-mechanical band-pass sigma-delta modulator control system for a MEMS gyroscope.