Effects of Spurious Modal Coupling on the Stability of Amplitude-Modulated Mode-Split Gyroscopes

The research discusses progresses and challenges towards the performance improvement of amplitude-modulated (AM) mode-split gyroscopes fabricated in commercial$30-\mu \mathrm{m}$-thick processes. From an existing 2.6$\text{mm}^{2}$sensor with$0.1^{\circ} / \sqrt{ } \text{hr}$angle random walk (ARW) and$5-10^{\circ} / \text{hr}$stability, the new architecture theoretically targets noise levels of$0.02^{\circ} / \sqrt{ } \text{hr}$and stability below$0.1^{\circ} / \text{hr}$, by increasing the area to$4.35\ \text{mm}^{2}$, doubling the rotor voltage, and triplicating the drive displacement. Experiments, however, while matching noise targets, reveal unexpected modal couplings, triggered by softening of high-order modes. This complex mechanism is modelled to explain the observed stability degradation.