Obtaining the fundamental and harmonic radiation conductances of a reflective SAW interdigital transducer

Abstract

The fundamental and harmonic radiation conductances of a solid-electrode uniform reflective SAW Interdigital transducer (IDT) are derived by applying the IDT reflection coefficient as a weighting function to modify the nominal (sin(X)/X)/sup 2/ radiation conductance. The IDT radiation conductance is derived from the single-tap SAW amplitude response function /spl mu//sub s/(f,/spl eta/)/spl ap//spl mu//sub s/(f/sub 0/,/spl eta/) sin[(/spl pi/f)/(2f/sub 0/)]P/sub n/(cos /spl eta//spl pi/), where P/sub n/=nth Legendre polynomial, together with IDT reflectivity as obtained from single-tap charge distribution analysis. The method is demonstrated for the fundamental and third-harmonic radiation conductances of a highly-reflective 100-MHz solid-electrode IDT using 41 electrodes with /spl eta/=0.25, on 128/spl deg/ YX-LiNbO/sub 3/. The results obtained by this approximate method are in good agreement with those published by Morgan (1998), using a quasi-static analysis applied to a reflective array model (RAM).