Effects of Synchronous Demodulation in Vibratory MEMS Gyroscopes: A Theoretical Study

In a vibratory microgyroscope, the synchronous demodulation of the secondary (sense) resonator output is a critical part of the signal processing. This is because different nonidealities can corrupt the resulting signals, including the angular velocity information. The effect of these nonidealities is revealed in the demodulation process. In this paper, issues related to synchronous demodulation are discussed. A detailed analysis of the effects caused by various nonidealities is provided. The nonidealities considered are as follows: delay in the displacement-to-voltage conversion, differences in the transfer functions of the two sidebands in the force-to-displacement conversion in the secondary resonator, nonlinearities in the displacement-to-voltage conversion, and mechanical-thermal noise. In addition to the analysis of the nonidealities, a general insight into the demodulation process, which is necessary for a successful system-level design, is provided.