Impact of Phase Noise on Bias Instability in Mode-Split Open-Loop MEMS Gyroscopes

Transient simulations are traditionally used to predict characteristics of MEMS gyroscopes. However, this time consuming and complex method yields little information about relationships between component parameters and system parameters as well as dominant sources of noise. This paper reports, analytical model for phase noise impact on bias instability of open-loop mode-split MEMS gyroscopes. This phase space based model is derived and analyzed. Its results are verified through transient simulation. Known noise sources have been considered and investigated for the influence on bias instability of MEMS gyroscopes. The model predicts PLL input noise to be a dominant contributor to the rate signal bias instability. The results of this work can be used to investigate the phase noise of any signal in the system. We further highlight the importance of the demodulation phase for the noise performance of the rate signal, using the model. This saves significant time when compared using the complex transient gyroscope models. Additionally, previously ignored complex transfer functions of components can now be explored. These are further validated with exemplary gyroscope parameters. The model is finally used to derive phase noise specification that fulfills defined requirements of a gyroscope.