SAW diffraction using angular-spectrum and Wigner functions

Diffraction significantly contributes to the operation of SAW devices in long filter structures, extended electrode configurations, and resonators. We use the ASPW and Wigner functions to simulate the diffraction of SAWs on typical anisotropic substrates. We employ a thin-element decomposition (TED) method, appropriately modified from that used in guided-wave optics, where the media are isotropic. In the TED method the calculational area is divided into two subdomains (metallized and free), perpendicular to the propagation direction and into thin imaginary columns along the propagation direction; diffraction is calculated separately in the subdomains and consecutively in each of the columns. The TED approach does not allow to take into account reflections from boundaries parallel to the primary direction of the wave. Such boundaries appear in SAW waveguides where wave propagation is usually calculated using guided-wave theory. We propose to incorporate reflections based on a generalization of the angular-spectrum representation, the Wigner distribution. The use of Wigner distributions seems especially advantageous in comparison with our implementation of the angular-spectrum representation, the TED method, since it will eliminate the need for a subdomain division