CAD modeling of SAW filters in mobile communication systems

Surface acoustic waves (SAWs) propagating in anisotropic and piezoelectric substrates have been investigated. The mass- and stress-loading effect, caused by two different isotropic and metallic films with finite thickness, is exactly taken into account by analyzing the multilayered structure. The mass density and the elastic stiffness constants of the metallic layers are determined by fitting calculated to measured velocity dispersion curves. High-precision group-delay-time measurements have been made. Thicknesses of the metallic films were measured with a transmission electron microscope. A least-square fit yields the unknown elastic constants and the densities of the aluminum and the aluminum oxide layer. These improved values of material constants are used in efficient computer-aided design (CAD) tools for high-performance SAW filter modeling and synthesis