High-frequency characterization for SAW interdigital transducers

Abstract

A new technique to accurately determine transmission line (TL) network parameters of surface acoustic wave (SAW) inter-digital transducers (IDTs) is presented. Various test IDTs and radio frequency (RF) filters for experimental characterizations are designed and fabricated on a LiTaO3 piezoelectric material. S-parameters for test devices were measured in the broad frequency bands of 50 MHz to 6 GHz. Then decoupling the acoustic waves from electromagnetic waves with an electro-mechanical coupling coefficient (k(2)), accurate TL circuit model parameters for SAW devices are determined. The acoustic wave model parameters are determined in an iterative manner by combining the measured S-parameters with a physical model. We show that SAW-based RF filters that operate at the frequency higher than 1 GHz can be very accurately designed using the proposed technique.