Excitation of SAW resonators and BAW-overmoded resonators by suspended IDT

We discuss here the possibility of using suspended metal electrodes for the excitation of surface acoustic wave (SAW) and single-mode bulk acoustic wave (BAW) resonator structures. The idea is, on one hand, to separate the driving electrodes from the piezoelectric substrate, being also the acoustic wave carrier substrate. While, on the other, to employ grooved surface gratings which can either reflect the SAW or convert it to resonant multimode BAW, respectively. The proposed approach is thought to eliminate mechanic losses caused by the electrodes, to reduce their parasitic ohmic resistance as well as to improve the resonator aging and power handling abilities. Further, the proposed approach enable the simultaneous use of periodical structures with different periodicity in such a way that one mode in a multimode BAW resonator can be selectively excited.