Micromechanical devices based on piezoelectric resonators
In some embodiments, a micromechanical filter includes multiple subfilters, each subfilter comprising multiple piezoelectric resonators mechanically coupled in series, wherein the subfilters are mechanically coupled to each other in parallel.
1. A micromechanical filter comprising:
multiple subfilters, including a first subfilter comprising first and second piezoelectric resonators mechanically coupled in series by a narrow coupling beam and a second subfilter comprising first and second piezoelectric resonators mechanically coupled in series by a narrow coupling beam;
a first narrow cross-coupling beam mechanically coupling the first piezoelectric resonator of the first subfilter to the first piezoelectric resonator of the second subfilter; and
a second narrow cross-coupling beam mechanically coupling the second piezoelectric resonator of the first subfilter to the second piezoelectric resonator of the second subfilter;
wherein the cross-coupling beams mechanically couple the first and second subfilters in parallel.
2. The micromechanical filter of claim 1 , wherein the piezoelectric resonators are disk resonators that operate in contour mode.
3. The micromechanical filter of claim 2 , wherein each disk resonator has a radius of approximately 5 to 500 μm.
4. The micromechanical filter of claim 1 , wherein the coupling beams each have a length of λ/4, wherein λ is the resonance wavelength of the subfilter.
5. The micromechanical filter of claim 1 , wherein the coupling beams each has have a length of λ/2, wherein λ is the resonance wavelength of the subfilter.
6. The micromechanical filter of claim 1 , wherein the first subfilter further includes a third piezoelectric resonator, the second and third piezoelectric resonators being mechanically connected by a further coupling beam.
7. The micromechanical filter of claim 6 , wherein the first subfilter further includes a fourth piezoelectric resonator, the third and fourth piezoelectric resonators being mechanically connected by a further coupling beam.
8. The micromechanical filter of claim 1 , wherein the cross-coupling beams each have a length of λ/4, wherein λ is the resonance wavelength of the subfilters.
9. The micromechanical filter of claim 1 , wherein the cross-coupling beams each have a length of λ/2, wherein λ is the resonance wavelength of the subfilters.
10. The micromechanical filter of claim 1 , wherein the piezoelectric resonators each comprise a bottom electrode, a top electrode, and a piezoelectric layer between the electrodes.
11. The micromechanical filter of claim 10 , wherein the piezoelectric resonators are constructed as piezoelectric-on-substrate resonators.
12. The micromechanical filter of claim 11 , wherein the filter is constructed on a silicon-on-insulator wafer comprising a handle layer, a buried oxide layer, and a device layer and wherein each resonator further comprises a portion of the device layer.
13. The micromechanical filter of claim 12 , wherein portions of the buried oxide layer positioned below the piezoelectric resonators are removed so that there is an air gap between the resonators and the handle layer.
14. A micromechanical filter comprising:
a first subfilter comprising first and second piezoelectric resonators mechanically coupled in series by a coupling beam, the coupling beam having a length of λ/4, wherein λ is the resonance wavelength of the subfilter;
a second subfilter comprising first and second piezoelectric resonators mechanically coupled in series by a coupling beam, the coupling beam having a length of λ/4;
a first cross-coupling beam mechanically coupling the first piezoelectric resonator of the first subfilter to the first piezoelectric resonator of the second subfilter; and
a second cross-coupling beam mechanically coupling the second piezoelectric resonator of the first subfilter to the second piezoelectric resonator of the second subfilter.
15. The micromechanical filter of claim 14 , wherein the first and second cross-coupling beams have a length of λ/4.
16. The micromechanical filter of claim 14 , wherein the first and second cross-coupling beams have a length of λ/2.
17. The micromechanical filter of claim 14 , wherein each piezoelectric resonator is a piezoelectric-on-substrate resonator including a bottom electrode, a top electrode, a piezoelectric layer between the electrodes, and a substrate on which the bottom electrode is formed.
18. The micromechanical filter of claim 17 , wherein the filter is constructed on a silicon-on-insulator wafer comprising a handle layer, a buried oxide layer, and a device layer, and wherein the device layer forms the substrate of each piezoelectric resonator.
19. The micromechanical filter of claim 18 , wherein portions of the barrier oxide layer positioned below the piezoelectric resonators are removed so that there is an air gap between the resonators and the handle layer.