Torsional resonator and filter using this
A torsional resonator for suppressing unnecessary flexural vibration and providing excellent resonance characteristic is provided. A vibrator is a beam structure or a paddle-like projection structure added onto a beam structure and an electrostatic force produced due to the potential difference between an electrode and the vibrator adds a moment with the axis of the beam of the vibrator as the center axis, but does not add a force for producing flexure to the beam. As one method, the same AC signal and DC bias voltages different in polarity are applied to an electrode pair of the electrode brought away from the vibrator and the electrode brought close to the vibrator with torsional vibration of the vibrator, so that only torsional vibration can be excited.
1. A torsional resonator comprising a vibrator for executing mechanical vibration and electrodes positioned close to the vibrator and having an electromechanical conversion function of converting voltage change between the vibrator and the electrodes into vibration of the vibrator,
wherein the vibrator comprises a beam structure, and
wherein the torsional resonator comprises a drive unit, which is configured so that an electrostatic force produced due to the potential difference between the electrodes and the vibrator produces a moment with the axis of the beam structure as the center axis, and is configured so as to apply DC bias voltages different in polarity and the same AC signal to an electrode pair of the electrodes, wherein the electrode pair includes one electrode brought away from the vibrator and one electrode brought close to the vibrator with torsional vibration of the vibrator.
2. The torsional resonator according to claim 1 , wherein the beam structure comprises a beam comprising projections at axially symmetric positions.
3. The torsional resonator according to claim 1 , wherein the beam structure comprises a paddle-like projection.
4. The torsional resonator according to claim 1 , further comprising two or more electrode pairs,
wherein the drive unit switches the polarity of the DC bias voltage applied to at least some electrodes of the electrode pairs, thereby switching torsional resonance between a low-order mode and a high-order mode.
5. The torsional resonator according to claim 1 , further comprising a plurality of the torsional resonators having different torsional resonance frequencies and a switch element for selecting at least one of the torsional resonators.
6. The torsional resonator according to claim 1 , further comprising a plurality of torsional resonators placed electrically in parallel.
7. The torsional resonator according to claim 1 , wherein the torsional resonator is housed in a case in which an atmosphere is sealed in a vacuum.
8. A filter using a torsional resonator according to claim 1 .