Lever mechanisms for anti-phase mode isolation in MEMS tuning-fork structures
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.
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,
wherein the anti-phase resonance levering system comprises a plurality of levers and a plurality of clamped-clamped beams, the plurality of levers coupled to the two resonating masses and to the plurality of clamped-clamped beams via a plurality of springs.
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-phase 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 the 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 the 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-phase 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 the 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 resonance mode (A) and in-phase (B) resonance mode, and two hybrid modes of resonance (C and D), each mode having a resonance frequency, where the four total masses are coupled pairwise by the anti-phase resonance levering system to stiffen the in-phase resonance mode (B), as well as one of the two hybrid modes (C), raising the frequency of the in-phase resonance modes B and one of the two hybrid modes C higher than the anti-phase resonance frequency.
17. The MEMS resonator of claim 1 where the two resonating masses and the 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 mode is left compliant,
wherein the anti-phase resonance levering system comprises a plurality of levers and a plurality of clamped-clamped beams, the plurality of levers coupled to the two resonating masses and to the plurality of clamped-clamped beams via a plurality of springs.
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.