Capacitive bulk acoustic wave disk gyroscopes
Capacitive bulk acoustic wave x, y and z-axes gyroscopes implemented on (100) and (111) silicon substrates are disclosed. Exemplary gyroscopes comprise a handle substrate, a bulk acoustic wave resonator element supported by the handle substrate, and a plurality of electrodes surrounding and separated from the resonator element by very small capacitive gaps. The electrodes can excite and detect at least two degenerate bulk acoustic wave resonant modes in the resonator. Advantages include reduced size; higher Q, which improves noise and bias stability; larger bandwidth, and improved shock resistance. In addition, the high Q is maintained in atmospheric or near-atmospheric pressure which reduces the cost and complexity of the wafer-scale packaging of the gyroscope.
1. Gyroscope apparatus, comprising:
a substrate having a plane;
a bulk acoustic resonator element; and
a plurality of electrodes surrounding and separated from the resonator element by a very small capactive gaps, which electrodes can excite and detect at least two degenerate bulk acoustic wave resonant modes in the resonator;
wherein the gyroscope apparatus senses rate or angle of rotation about at least one axis in the plane of the substrate.
2. The apparatus recited in claim 1 wherein the substrate supports the bulk acoustic resonator element.
3. The apparatus recited in claim 1 wherein the capacitive gaps are on the order of 200 nanometers or less.
4. The apparatus recited in claim 1 further comprising direct current and alternating current voltage sources for the excitation and tuning of the apparatus.
5. The apparatus recited in claim 1 wherein the resonator element is a disk-shaped structure made of a polysilicon or single-crystalline silicon.
6. The apparatus recited in claim 1 wherein the resonator has a bulk acoustic wave resonant frequency which is at least 1 MHz.
7. The apparatus recited in claim 1 further comprising support electronics for excitation, readout and turning of the resonator element.
8. The apparatus recited in claim 1 wherein at least three bulk acoustic resonator elements and corresponding pluralities of electrodes are integrated on a single substrate to sense rate or angle of rotation about three orthogonal axes.
9. Gyroscope apparatus, comprising:
a handle substrate;
a disk resonator element supported by the handle substrate;
a plurality of electrodes surrounding and separated from the disk resonator element by very small capacitive gaps, which electrodes can excite and detect at least two degenerate bulk acoustic wave resonant modes in the disk resonator; and
support electronics for excitation, readout and tuning of the disk resonator.
10. The apparatus recited in claim 9 wherein the capacitive gaps are on the order of 200 nanometers or less.
11. The apparatus recited in claim 9 wherein the disk resonator has a bulk acoustic wave resonant frequency which is at least 1 MHz.
12. The apparatus recited in claim 9 wherein the disk resonator is supported by the handle substrate at its center.
13. The apparatus recited in claim 9 wherein the disk resonator is aligned with a support element at a center of the disk resonator.
14. The apparatus recited in claim 9 wherein the disk resonator is perforated.
15. The apparatus recited in claim 9 which senses rate or angle of rotation about a vertical axis perpendicular to the plane of the substrate.
16. The apparatus recited in claim 9 which senses rate or angle of rotation about at least one axis in the plane of the substrate.
17. The apparatus recited in claim 9 wherein one or more resonator elements and one or more pluralities of electrodes and support electronics are integrated on a single substrate to form an integrated inertial measurement unit.