Analysis and Compensation of Electrical Feedthrough Effect on Scale Factor of Force-to-Rebalanced MEMS Gyroscopes

In this article, we report an analytic model describing the phenomenon that, if electrical feedthrough exists between the actuating and the readout electrodes of the sense mode, the scale factor of force-to-rebalanced microelectromechanical system (MEMS) gyroscopes will drastically vary with the change of the frequency split between the drive mode and the sense mode. In contrast to the feedthrough from the actuating voltage of the drive mode, whose amplitude is small due to the high Q value of resonators, the amplitude of the sense-mode actuating voltage depends on the angular rate to be measured and has significant impacts on scale factors. The electrical feedthrough in the sense mode provides an additional signal path affecting the feedback coefficient of the angular rate measurement. For different electrical feedthrough coefficients and frequency splits, the resultant closed-loop scale factor may vary by a factor of several and even change its polarity. The presented model is validated by numerical simulations and experiments and demonstrates good consistency. Besides, we present a real-time feedthrough compensation algorithm based on the off-resonant signal injection. By injecting a double-side modulated signal with a constant magnitude, the feedthrough coefficient can be extracted from the loop and, then, can be compensated accordingly. The experiments demonstrate that, with a feedthrough capacitance of 26fF, the fluctuation of the compensated closed-loop scale factor with the frequency split variation mitigates by a factor of 55 times.