Modeling of Phase Noise in Mode-Split Open-Loop MEMS Gyroscopes

This paper investigates demodulation phase noise of an open-loop, mode-split MEMS gyroscope. A method to convert a model of an amplitude-modulated gyroscope into a base-band phase space model is provided. We highlight the importance of holistic phase space analysis and distinguish between well-known oscillator phase noise and, as analyzed in this study, phase noise of the angular rate demodulation. A literature review revealed the most probable noise sources for such a model. We found that any possible phase flicker noise source on the input of the PLL, for example from capacitance-to-voltage converter, analog-to-digital converter or the phase detector, would be transferred to directly become demodulation phase flicker noise. As a result, bias instability would be created. Lastly, we discuss possibilities to experimentally validate the proposed model.