An Analysis to Improve Stability of Drive-Mode Oscillations in Capacitive Vibratory MEMS Gyroscopes

This paper presents an analysis showing that it is possible to determine the factors that limit the stability of drive-mode oscillations of a vibratory MEMS gyroscope with precise modeling. Specifically, unwanted electrical resonance characteristics of the gyroscope drive-mode are analyzed together with analytical expressions, whereas the results of the theoretical analyses are verified both by simulations and measurements, which agree very well. It is demonstrated that the stability of the drive-mode oscillations significantly improves by using a compensation capacitor across resistive preamplifiers of drive-mode oscillator output when the oscillator is driven by square-wave input signal generated by conventional automatic gain control (AGC) loops. The model can be used to identify and eliminate other factors that limit the bias stability.