Direct finite element analysis of SAW filter frequency response

摘要

A direct element model is developed for the full-scale analysis of electromechanical phenomena involved in SAW devices. The equations of wave propagation in piezoelectric materials are discretized using the Galerking method, in which an implicit algorithm of the Newmark family with unconditional stability is implemented. The Rayleigh damping coefficients are included in the elements near the boundary to reduce the inflence of the reflection of waves. The performance of the model is demonstrated by the analysis of the frequency response of a YZ-lithium niobate filter with two uniform ports, with emphasis on the influence of the number of electrodes. The frequency response of the filter is obtaind through the Fourier transform of the impulse response, which is solved directly from the finite element simulation. It shows that the finite element results are in good agreement with th characteristic frequency reponse of the filter predicted bu the simple phase-matching argument. The ability of the method to evaluate the influence of the bulk waves at the high-frequency end of the filter passband and the inflence of the number of electrodes on insertion lass is noteworthy. We conclude that the direct finite element analysis of SAW devices can be used as an effective tool for the design of high performance SAW devies. Some practical computational challenges of finitie element modeling of SAW devices are discussed.