Electrostatic Frequency Tuning of Bulk Acoustic Wave Disk Gyroscopes

Abstract

Bulk acoustic wave gyroscopes have been researched for potential benefits such as immunity to shock and vibration and the high Q factors achievable with the bulk modes. This paper outlines an approach to address mode matching in bulk acoustic wave (BAW) disk gyroscopes using electrostatic frequency tuning. Electrostatic frequency tuning is achieved by varying the potential difference between the body of the resonator and electrodes surrounding the disk resonator. Tuning of the frequencies of both drive and sense modes is demonstrated in this work as a means to achieving mode matching. The experimental results are also compared to COMSOL simulations reporting mode matching.

A Silicon MEMS Disk Resonator Oscillator Demonstrating 36 ppt Frequency Stability

“…The disk is surrounded by 12 identical electrodes and employs edge anchoring. The characterisation of the resonant modes for this device has revealed several modes with quality factors exceeding a million [12], [18] and a Q-f metric exceeding 10 13 . The frequency response showing all in-plane modes between 500 kHz to 2 MHz is presented in Fig.…”

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

“…DEVICE The device-under-test in this study is a vacuum packaged micromachined disk gyroscope fabricated in a (100) single crystal silicon (SCS) substrate using a silicon-on-insulator (SOI) MEMS process employing wafer-level vacuum encapsulation [22]. The characterisation of resonant modes for this device has revealed several modes with quality factors exceeding a million [10], [15] and a Q-f metric exceeding 10 13 . Fig.…”

“…The mode shapes and resonant frequencies of inplane vibration modes can be estimated theoretically using two dimensional elastic theory [23]. Reference [15] presents the systematic approach to experimentally characterize these modes. The key design parameters and simulation results of the device are summarized in Table I.…”

“…In such cases, electrostatic frequency tuning can be employed to achieve mode matching [8]. Due to the high mechanical stiffnesses associated with the BAW modes, it can be difficult to compensate for even small mismatches in the natural frequencies: in order to overcome this problem, understanding the alignment of the mode shapes with the peripheral electrodes is necessary as it enables a systematic approach to mode matching using electrostatic frequency tuning, details of which are presented elsewhere [15].…”

Characterization of Modal Frequencies and Orientation of Axisymmetric Resonators in Coriolis Vibratory Gyroscopes

“…Microelectromechanical system (MEMS) Coriolis vibratory gyroscopes (CVGs) have been revealed enormous potential for high-end applications, even for the applications of near-navigation grade [1][2][3][4][5]. Among the MEMS gyroscopes with the top performances, the MEMS CVGs with axisymmetric resonators, for instance, ring [6] or disk [7][8][9], hemispherical [10][11][12], and quad-mass [13][14][15] resonators, are particularly appealing by virtue of their angular rate-integrating ability, which offers benefits of high dynamics, wide ranges, and shock and vibration resistance. Besides, the symmetry in the structure of the resonators provides possibilities of various in-run calibration and compensation algorithms in the control system [16][17][18][19], further improving the bias and the scale factor performances for the gyroscopes.…”