Analysis of SAW reflection

A study of perturbative and variational approaches is carried out for SAW (surface acoustic wave) reflections. It is shown that the perturbation treatment and variational formulation are mutually consistent. These two approaches yield nearly identical results for the reflection coefficients and velocity shifts due to metal finger and groove overlays. The on- and off-resonance behavior of the reflection coefficient can be described correctly using either one of these theories, with inclusion of the overlay shape dependence to account for off-resonance effects. The variational approach lends itself more readily to analysis of arbitrary grating structures since no complicated boundary terms appear, and it also can include higher-order effects neglected in first-order perturbation theory by a judicious choice of the trial function. But the utility of the variational principle is limited in calculating physically meaningful results by the accuracy of the trial functions used