Boundary element method analysis of interdigital transducers having arbitrary metallisation ratio

Abstract

The paper describes the use of weighted Tchebycheff-polynomials as the expansion functions for the boundary element method, by which SAW-IDTs with arbitrary metallisation ratio r (finger width relative to finder periodicity) were analysed. First, it is shown that the order of the polynomials N should be increased with r to keep the accuracy within a specified value: N=2 results in negligible error for commonly employed IDTs with r of less than 0.9. Secondly, the r dependence of IDT input admittance was analysed and IDT behaviours were characterised at both fundamental and harmonic frequencies. © 1991 The Japan Society of Applied Physics.