An Analysis of SAW Interdigital Transducers with Internal Reflections and the Application to the Design of Single-Phase Unidirectional Transducers

Abstract

A new coupling-of-modes (COM) analysis of SAW interdigital transducers (IDTs) is presented. The analysis includes the effects of multiple reflections within a transducer. The fundamental equations are derived and some simple closed-form results a re given. In addition, some general properties having regard to the relative phase of transduction and reflection c oefficients within a transducer are derived. A new class of unidirectional transducers is proposed which require only one matching network and do not have the crossovers required in current three-phase designs. These single-phase unidirectional transducers (SWDTs) utilize internal r eflections within the transducer to achieve unidirectional behavior. Practical SWDT configurations are proposed and some experimental results presented. The application of the new COM analysis to synthesis is discussed.