P5H-1 Hybrid Finite Element Analysis of Leakey Surface Acoustic Waves in Periodic Waveguides of Finite Thickness

A numerical approach based on the hybrid finite element method is developed for the analysis of traveling SAW/LSAW in periodic waveguides of finite thickness. The method combines conventional finite elements for the inhomogeneous region including electrodes and modal expansions for the homogeneous substrate region. The wave reflection at the bottom surface of the substrate is taken care by enforcing the traction-free condition for each space harmonic in the modal expansion. Since some of the expansion components are exponentially increasing into the depth of the substrate, a very bad floating point overflow problem plagues the HFEM code. To avoid the floating point overflow problem when the traction-free condition is enforced, we propose an "adaptive wave amplitude allocation." The simulated dispersion curves and temperature characteristics of leaky SAWs on quartz substrates of finite thickness are presented.