Admittance matrix of a surface acoustic wave interdigital transducer.

The admittance matrix of a surface acoustic wave interdigital transducer (IDT) is derived from the impulse response model and circuit theory. It is shown, that Y(23)=Y(13) for a symmetrical IDT and Y(23)-Y(13) for an antisymmetrical one. A simple algorithm for the input admittance calculation of apodized IDTs is given. The proposed algorithm is also capable of analyzing withdrawally weighted, withdrawally weighted and apodized, and unapodized IDTs. Calculations of an apodized IDT input admittance are compared with measurements.