Precise modeling of complex SAW structures using a perturbation method hybridized with a finite element analysis

Abstract

Surface acoustic wave (SAW) devices used in high stability oscillators or filters are generally designed to exhibit a low sensitivity to thermal and mechanical perturbations. Theoretical developments based on variational equations have been proposed to model these phenomena. Mechanical perturbations applied to simple geometries of the propagation substrate can be analytically considered using this approach. However, because of the strong dependence of mechanical effects on the geometry of the substrate, analytical models cannot provide realistic predictions on complex SAW structures subject to external stresses, vibrations, or accelerations. In this paper, an adaptation of the Tiersten-Sinha perturbation method is proposed, which combines the finite element analysis (for a precise prediction of quasi-static perturbations) and analytical variational equations of SAW propagation. Comparison of results obtained using simple analytical model and the proposed approach shows a very good agreement in the case of symmetrical radial in-plane compression on circular plates and monoaxial bending moments applied on rectangular substrates. This validation enables the consideration of more complicated configurations and allows using special stress-compensated SAW quartz cuts.