LEVER MECHANISMS FOR ANTI-PHASE MODE ISOLATION IN MEMS TUNING-FORK STRUCTURES

• US 20140260615A1
• Filed: 03/15/2013
• Published: 09/18/2014
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Regents of the University of California (University of California)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: Trusov, Alexander A., Simon, Brenton R., Shkel, Andrei M.
• Granted Patent: US 9,217,756 B2
• Time in Patent Office: Days
• US Class Current: 73/514.29
• CPC Class Codes: G01C 19/5621 the devices involving a micromechanical structure
• CPC Class Codes: G01P 15/097 by vibratory elements
• CPC Class Codes: H03H 2009/02496 Horizontal, i.e. parallel to the substrate plane
• CPC Class Codes: H03H 9/2463 Clamped-clamped beam resonators
• CPC Class Codes: H03H 9/2468 Tuning fork resonators

Abstract

A MEMS resonator includes two resonating masses having an anti-phase and in-phase resonance mode, each mode having a resonance frequency, and an anti-phase resonance levering system coupled to the two resonating masses to stiffen and/or dampen the in-phase resonance mode while leaving the anti-phase resonance mode compliant. This effectively raises the in-phase resonance frequency above the anti-phase resonance frequency, and potentially creates a large frequency separation between the two resonance modes. This reduces the energy transfer between the two modes, allowing for robustness to external acceleration, because the in-phase mode is of a higher frequency. The anti-phase resonance levering system is disposed between the two resonating masses as an internal levering mechanism, or is disposed around the two resonating masses as an external levering mechanism.

Claims

1. A MEMS resonator comprising:

two resonating masses having an anti-phase and in-phase resonance mode, each mode having a resonance frequency; and

an anti-phase resonance levering system coupled to the two resonating masses to stiffen and/or dampen the in-phase resonance mode while leaving the anti-phase resonance mode compliant by effectively raising the in-phase resonance frequency above the anti-phase resonance frequency, and potentially creating a large frequency separation between the two resonance modes, so that energy transfer is reduced between the two modes, allowing for robustness to external acceleration, because the in-phase mode is of a higher frequency.

2. The MEMS resonator of claim 1 where the anti-phase resonance levering system is disposed between the two resonating masses as an internal levering mechanism.

3. The MEMS resonator of claim 1 where the anti-phase resonance levering system is disposed around the two resonating masses as an external levering mechanism.

4. The MEMS resonator of claim 2 where the anti-phase resonance levering system further comprises an external levering mechanism disposed around the two resonating masses.

5. The MEMS resonator of claim 2 where the internal levering mechanism is incorporated into a quadruple mass device to reduce quadrature between the anti-phase and in-phase resonance mode

6. The MEMS resonator of claim 1 where the levering system is used in an FM accelerometer with a large, non-linear mechanical scale factor by setting the in- and anti-phase resonance frequencies close together.

7. The MEMS resonator of claim 1 formed on a substrate, where the anti-phase resonance levering system comprises a clamped-clamped beam coupling between the two masses so that the stiffness and damping of the in-phase resonance mode and induced force within the clamped-clamped beam coupling produces a positive frequency drift with increasing temperature, where the stiffness and damping and induced force combine to produce at least a first-order temperature drift cancellation of the mismatch in the thermal expansion coefficients between the material of the resonator and the substrate.

8. The MEMS resonator of claim 7 where the damping of the anti-phase resonance mode remains high compared to that of the damping of the in-phase resonance mode.

9. The MEMS resonator of claim 1 where the anti-phase resonance levering system increases the Q-factor of the anti-phase resonance mode by reducing the impact of structural asymmetries.

10. The MEMS resonator of claim 1 formed on a substrate, where temperature robust resonance frequencies are achieved by fabricating the two masses and anti-phase resonance levering system, on one hand, and the substrate, on the other hand from materials with different thermal expansion coefficients.

11. The MEMS resonator of claim 1 where the two masses and anti-phase resonance levering system comprise a tuning fork assembly, accelerometer or gyroscope.

12. The MEMS resonator of claim 1 where the anti-phase resonance levering system causes simple linear displacement in anti-phase motion, and induces torque in in-phase motion.

13. The MEMS resonator of claim 1 where the anti-phase resonance levering system has a greater resistance to torque than displacement, so that the in- and anti-phase resonance frequencies can be swapped, and the in-phase frequency resonance increased.

14. The MEMS resonator of claim 1 where the anti-phase resonance levering system comprises a clamped-clamped beam coupling between the two masses.

15. The MEMS resonator of claim 1 where the two resonating masses and an anti-phase resonance levering system comprises a Coriolis vibratory gyroscope.

16. The MEMS resonator of claim 3 further comprising two additional resonating masses for a total of four resonating masses having an anti-phase mode (A) and in-phase (B) resonance mode, and two hybrid modes of resonance (C and D), each mode having a resonance frequency, where masses are coupled pairwise by the anti-phase resonance levering system to stiffen the in-phase resonance (B), as well as one of the hybrids (C), raising the frequency of modes B and C higher than the anti-phase resonance frequency.

17. The MEMS resonator of claim 1 where the two resonating masses and an anti-phase resonance levering system comprises an FM accelerometer having a scale factor, where the anti-phase resonance levering system is arranged and configured to set in-phase and anti-phase resonance frequency of the two resonating masses close together with the anti-phase resonance frequency placed lower in comparison to allow the anti-phase resonance to be the first mode to fail through physical contact of the masses, and thus allowing for the observation of the non-linear stiffness effect on the increase in scale factor with displacement.

18. A MEMS resonator comprising:

two resonating masses having an anti-phase and in-phase resonance mode, each mode having a resonance frequency; and

an anti-phase resonance levering system coupled to the two resonating masses, where the in-phase resonance frequency is higher than the anti-phase resonance frequency, while the anti-phase resonance is left compliant.

19. The MEMS resonator of claim 18 where the anti-phase resonance levering system is disposed between the two resonating masses as an internal levering mechanism.

20. The MEMS resonator of claim 18 where the anti-phase resonance levering system is disposed around the two resonating masses as an external levering mechanism.

21. The MEMS resonator of claim 19 where the anti-phase resonance levering system further comprises an external levering mechanism disposed around the two resonating masses.