FIRST-ORDER VELOCITY SHIFT AND REFLECTION COEFFICIENT FOR SURFACE-ACOUSTIC-WAVE PROPAGATION

Design of surface acoustic wave (SAW) devices requires accurate values of velocity shift q and reflection coefficient r associated with fing er overlays placed on the substrate material. In previous treatments v ariational and perturbative approaches have been developed for calcula ting first-order reflection coefficients and velocity shifts; however, the anisotropic substrate materials have until now been modeled by an effective isotropic substrate. We extend the variational and perturba tive calculations of the first-order quantities to fully anisotropic c rystals for several standard SAW substrate and overlay materials. More over, we report results obtained with both electrically free and short ed trial functions, and suggest optimum parametrizations of q and r, t o first order in h/lambda, where h is the finger thickness and lambda is the Rayleigh wavelength. (C) 1996 American Institute of Physics.