Piezoelectric rotational MEMS resonator
This disclosure reveals a resonator where at least one suspended inertial mass is driven into rotational oscillation by a piezoelectric drive transducer, or where the rotational motion of at least one suspended inertial mass is sensed by a piezoelectric sense transducer. The disclosure is based on the idea of suspending the inertial mass with a one-sided suspender arrangement, where only one suspender is attached to each anchor point, and on the optimal positioning of the suspender in relation to the effective center of gravity of the resonator. The resonator may be employed in a resonator system, a clock oscillator or a gyroscope.
1. A rotational resonator comprising:
a substrate with one or more anchor points and an inertial mass with a first longitudinal end and a second longitudinal end,
wherein the inertial mass is suspended from the one or more anchor points by one or more suspenders extending from the one or more anchor points toward either the first longitudinal end or the second longitudinal end of the inertial mass,
wherein one or more of the suspenders are coated with a piezoelectric transducer structure configured to drive or detect oscillating rotary movement in the inertial mass, and
wherein no more than one suspender is attached to any of the anchor points, and that the longitudinal length of each coated suspender is 0.5-1 times the longitudinal length of the inertial mass.
2. A rotational resonator according to claim 1 , wherein the distance from either the rotation axis of the inertial mass, or from the transversal line which crosses the rotation axis of the inertial mass, to the effective center of gravity of the resonator does not exceed 0.01 times the length of any of the one or more coated suspenders at any point in the oscillation cycle.
3. A rotational resonator according to claim 2 , wherein each of the one or more coated suspenders have an even transversal breadth profile and even vertical height profile along the entire longitudinal length of the suspender and that the longitudinal distance on each coated suspender from the anchor point to which it is attached to the transversal line which passes through the effective center of gravity of the resonator is 0.49-0.51 times the length of the coated suspender.
4. A rotational resonator according to claim 1 , wherein the number of suspenders is one.
5. A rotational resonator according to claim 4 , wherein the inertial mass comprises one internal opening and that one anchor point and one suspender is located in this internal opening.
6. A rotational resonator according to claim 4 , wherein the inertial mass comprises one external opening and that one anchor point and one suspender is located in this external opening.
7. A rotational resonator according to claim 1 , wherein the number of anchor points is at least two and the number of suspenders is at least two.
8. A rotational resonator according to claim 7 , wherein the inertial mass comprises at least two external openings and that one anchor point and one suspender is located in at least two of the external openings.
9. A rotational resonator according to claim 7 , wherein the inertial mass comprises at least two internal openings and that one anchor point and one suspender is located in at least two of the internal openings.
10. A rotational resonator according to claim 7 , wherein the inertial mass comprises at least one internal opening and that at least two anchor points and at least two suspenders are located in the same internal opening.
11. A rotational resonator according to claim 7 , wherein all of the at least two suspenders extend toward the same longitudinal end of the inertial mass from their respective anchor points.
12. A rotational resonator according to claim 7 , wherein at least one of the at least two suspenders extends from its anchor point toward a first longitudinal end of the inertial mass, while another of the at least two suspenders extends from its anchor point toward a second longitudinal end of the inertial mass.
13. A rotational resonator according to claim 1 , wherein at least one of the coated suspenders is coated with a piezoelectric transducer structure configured to drive or detect in-plane rotational oscillation.
14. A rotational resonator according to claim 1 , wherein at least one of the coated suspenders is coated with a piezoelectric transducer structure configured to drive or detect out-of-plane rotational oscillation.
15. A rotational resonator according to claim 1 , wherein at least one of the coated suspenders is coated with a piezoelectric transducer structure configured to drive or detect in-plane rotational oscillation and also with a piezoelectric transducer structure configured to drive or detect out-of-plane rotational oscillation.