A quasi-field equivalent circuit of an interdigital transducer of surface acoustic waves

A new equivalent circuit of a surface-acoustic-wave (SAW) interdigital transducer (IDT) is proposed. A method using this circuit for calculation of the device's gain-frequency characteristic and impedance is described. The fingers of the transducer can be arbitrarily shaped and positioned. The electrode current is obtained via the rigorous calculation of the SAW-related charge in the piezoelectric substrate and of the charge induced by the former charge in the transducer electrodes. The method allows design of SAW devices with an arbitrary complex finger structure and a multilayer substrate.