A NEW APPROACH TO CHARACTERIZING ACOUSTIC WAVES PROPAGATING UNDER A PERIODICALLY ELECTRODED ARRAY ON PIEZOELECTRIC SUBSTRATE

Abstract
The coupling problem between electrodes owing to acoustic wave propagation and electrostatic effect in a periodic metal grating on a piezoelectric substrate is theoretically studied. Harmonic admittance approach is used to obtain the complete acoustic wave spectrum, and mutual admittance is taken to describe wave propagation properties under the grating. Analytical expression for the contribution of surface wave (SAW) is proposed, and its characteristic parameters are numerically determined. A particular feature of the present study consists of using a particular curve-fitting technique to deal with a leaky SAW as well as a conventional Rayleigh SAW. The accurately determined SAW's parameters allow to correctly remove the participation of SAW from the global coupling, so makes it easier to analyze the spurious bulk waves (BAW), especially the surface skimming bulk waves (SSBW) in such devices. The plot as a function of propagation distance, n, of the BAW mutual admittance shows that the BAW's amplitude in the far-field varies according to a power law, i.e., n^-p, the value of p strongly depends on the substrate configuration.