A novel demodulation algorithm for MEMS gyroscope digital control system

In order to further improve the performance of MEMS gyroscope, a novel demodulation algorithm all-phase Fast Fourier Transform (apFFT) based on FPGA is proposed to the digital control system, in which the drive detection signal and sensitive axis signal are demodulated respectively. Combining with automatic gain control (AGC) and phase-locked loop (PLL), the closed-loop drive control and high precision demodulated output of MEMS gyroscope have been implemented. A printed circuit board based on FPGA is manufactured and the corresponding experiment is carried out. The experimental results indicate that the digital control system with the apFFT demodulation algorithm of MEMS gyroscope achieves good performance. The amplitude variance of drive detection signal at room temperature is less than 2ppm. The relative error of phase difference between drive signal and drive detection signal is 33ppm. The bias stability of tested MEMS gyroscope is 2.62deg/h with the scale factor being 7.95mV/deg/s. The tested gyroscope with all-phase FFT demodulation algorithm has a better ARW performance of 0.16deg/h/Hz^1/2 than that using multiplication demodulation algorithm with ARW performance of 1.04deg/h/Hz^1/2. The Experiment verifies that the proposed apFFT demodulation algorithm is feasible and effective.