Effect of EAM on Capacitive Detection of Motion in MEMS Vibratory Gyroscopes

The Electromechanical Amplitude Modulation (EAM) is frequently used to eliminate feed-through signals between forcer and pick-off electrodes of resonant microstructures. However, there are some undesirable effects of EAM that need to be considered. This work studies the contribution of EAM on dissipation of energy and appeared non-linear dynamics in MEMS Coriolis Vibratory Gyroscopes (CVGs). We presented an analytical model, capturing the effect of AC carrier signal on amplitude-frequency coupling, scale factor instability, and in-run noise performance of CVGs. The effect of EAM on a Dynamically Amplified dual-mass Gyroscope (DAG) was experimentally demonstrated and compared to the simulation results of the analytical model. We concluded that the AC carrier signal in EAM influences the amplitude-frequency couplings along both the drive and sense modes of the gyroscope through modifying the non-linear electrostatic stiffnesses, which was also proven to be one of the dominant sources of both the scale factor nonlinearity and frequency instability in the near-mode-matched DAG, operating in the open-loop rate mode.