Zero-Rate-Output Instability Phenomena in MEMS Gyroscopes with and Without Quadrature Nulling

This work investigates instability phenomena in amplitude modulated gyroscopes with sub 0.1°/hr bias stability and 0.03°/√ hr angle random walk. A predictive model is developed for the dependence of the zero-rate output (ZRO) on temperature for both the condition of uncompensated quadrature, and, notably, also for the case of quadrature nulled by an automatic loop with electromechanical electrodes. The model verification requires an accurate calibration of various parameters: other than the usual ones (resonance, quality factor, split value...), the work also includes a temperature characterization of the feedthrough capacitances and of quadrature, on dozens of samples. The model predicts ZRO variations in closed-loop quadrature to depend more on scale-factor changes and drive-sense feedthrough, rather than on quadrature or phase changes, which are instead known main contributors in absence of quadrature null. Experiments are taken both as ZRO vs temperature curves and as Allan deviations in controlled conditions: results confirm some of the model suggestions, but highlight additional phenomena, not captured by the model, like stability dependence on drive amplitude, and Random Telegraph Noise (RTN).[2026-0058]