Suppression of bulk-scattering loss in SAW resonator with quasi-constant acoustic reflection periodicity

The author proposes a SAW (surface acoustic wave) resonator structure which suppresses the bulk-scattering loss for a high reflectivity resonator. The approach uses an effective configuration to cancel the scattered radiation bulk waves from the GRs (grating reflectors) and the IDT (interdigital transducer) simultaneously. It consists of an IDT and metal-strip GRs, which are of the same material and which have the same thickness. The distance between the IDT and the GR is set to be a half-wavelength and the pitch for the IDT electrodes is slightly shortened to tune to the resonance condition. The structure realizes quasiconstant acoustic reflection periodicity (QARP) all over the resonator. The QARP structure was shown to suppress the mode conversion loss and to improve the resonator Q-factor. Experimental results provide that the QARP structure led to a two-fold improvement of the Q-factor for the high reflectivity resonator. Furthermore, theoretical analysis also proved that the scattered bulk waves were suppressed to less than 1/100 in the QARP-structured SAW resonator