Piston mode generation in thin plate lamb wave device
An acoustic wave resonator comprises a plurality of interdigital transducer (IDT) electrodes disposed on upper and lower sides of a piezoelectric film, the IDT electrodes on the upper side of the piezoelectric film being offset from the IDT electrodes on the lower side of the piezoelectric film by λ/4, λ being a wavelength of a main acoustic wave generated by the acoustic wave resonator to enable the acoustic wave resonator to generate piston mode acoustic waves responsive to electrical excitation of the plurality of IDT electrodes with an alternating current.
1 . An acoustic wave resonator comprising a plurality of interdigital transducer (IDT) electrodes disposed on upper and lower sides of a piezoelectric film, the IDT electrodes on the upper side of the piezoelectric film being offset from the IDT electrodes on the lower side of the piezoelectric film by λ/4, λ being a wavelength of a main acoustic wave generated by the acoustic wave resonator to enable the acoustic wave resonator to generate piston mode acoustic waves responsive to electrical excitation of the plurality of IDT electrodes with an alternating current, the plurality of IDT electrodes being electrically coupled to a frequency generator and phase shifter that causes a phase of an excitation voltage applied to the IDT electrodes on the upper side of the piezoelectric film to be phase shifted from an excitation voltage applied to the IDT electrodes on the lower side of the piezoelectric film by greater than zero degrees and up to 90°.
2 . The acoustic wave resonator of claim 1 wherein the piezoelectric film includes aluminum nitride.
3 . The acoustic wave resonator of claim 2 wherein the piezoelectric film has a thickness of between 0.1λ and 1.0λ.
4 . The acoustic wave resonator of claim 2 wherein the piezoelectric film has a thickness of between 0.3λ and 0.5λ.
5 . The acoustic wave resonator of claim 1 wherein the plurality of IDT electrodes each have a thickness of between about 0.01λ and about 0.03λ.
6 . The acoustic wave resonator of claim 1 included in an electrical module having the frequency generator and phase shifter that causes the phase of the excitation voltage applied to the IDT electrodes on the upper side of the piezoelectric film to be phase shifted from the excitation voltage applied to the IDT electrodes on the lower side of the piezoelectric film.
7 . The acoustic wave resonator of claim 1 included in an electrical module having the frequency generator and phase shifter that causes the phase of the excitation voltage applied to the IDT electrodes on the upper side of the piezoelectric film to be phase shifted by 90° from the excitation voltage applied to the IDT electrodes on the lower side of the piezoelectric film.
8 . The acoustic wave resonator of claim 1 having a resonant frequency above 5 GHz.
9 . The acoustic wave resonator of claim 8 having a resonant frequency above 6.5 GHz.
10 . The acoustic wave resonator of claim 8 having a resonant frequency above one of 9 GHz or 9.2 GHz.