Field analyses of thickness shear bulk acoustic resonators with different electrode edge ratio using full three dimensional finite element method simulation

Abstract

Abstract This paper is aimed at revealing origins of spurious resonances and Q deterioration of thickness shear bulk acoustic resonators (TSBARs) with the edge ratio W x /W y of rectangular electrodes by a field analyses. Here, W x and W y are distances between side edges giving the broadband and standard piston designs, respectively. The field distribution is calculated by applying traceback technique to the full three dimensional finite element method based on hierarchical cascading technique, its variation with the edge ratio is studied in detail, with assistance of the wavenumber domain analysis. The result indicates that the mode conversion and the leakage occur at the bump region causing Q reduction, and generated hybrid modes causing spurious resonances. The former is significant when W x /W y is large and the latter becomes obvious when W x /W y is small.