A self-clocked readout circuit for MEMS gyroscope to avoid frequency aliasing

The performance of MEMS gyroscope is susceptible to the interface circuits. It is reported in the published literature that traditional interface circuits adopted modulation and demodulation technique to detect the signal of MEMS gyroscope. The frequencies of carrier waves are not sensitive to external environment which are created by an external crystal, while the resonant frequency of the gyroscope is sensitive to temperature. In this case, there will be frequency aliasing between the secondary demodulation signal and the vibrating gyroscope signal. The frequency aliasing may have a certain negative effect on zero-bias of MEMS gyroscope. In this paper, a self-oscillation loop in vibrating gyroscope was proposed based on the phase locked loop (PLL). This self-clocked interface circuit can track the primary frequency of gyroscope instead of an external crystal so that the negative effect caused by temperature changes can be almost eliminated. Comparison was made between the experimental results of traditional and improved PCB circuit, which proved that the frequency aliasing was almost solved and the results of simulation and experiment showed an obvious improvement on the zero-bias of gyroscope.