Sub-Deg-per-Hour Edge-Anchored Bulk Acoustic Wave Micromachined Disk Gyroscope

This paper reports on the experimental characterization of a vacuum packaged bulk acoustic wave disk gyroscope with T-shape anchors fabricated on a (100) single-crystal silicon substrate. Improvements in key device performance parameters are achieved by implementing mode matching using electrostatic frequency tuning to decrease the frequency split between two near-degenerate bulk acoustic modes from 4 Hz to 0.4 Hz. Gyroscopic operation is demonstrated by driving one of the secondary degenerate elliptical modes while sensing the response in the other elliptical mode, both demonstrating quality factors exceeding 1 million at an operating frequency of ~976 kHz. As a result, the mechanical sensitivity of the gyroscope is improved by a factor of 7.76 times for near mode-matched operation relative to the case with no tuning of the frequency spacing between the modes. Additionally, the angle random walk and bias instability were improved from 0.042 °/√h to 0.037 °/√h and 1.65 °/h to 0.95 °/h respectively, benchmarking favorably with respect to the state-of-the-art of BAW disk gyroscopes. [2021-0151]