High-frequency characterization for SAW interdigital transducers

A new technique to accurately determine transmission line (TL) network parameters of surface acoustic wave (SAW) interdigital 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 (k2\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$k^{2}$$\end{document}), 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.