Considerations of SAW coupled-mode equations and equivalent circuit representation of interdigital transducers

A simple equivalent circuit representing the whole structure of an interdigital transducer (IDT) is derived from the coupling-of-mode (COM) equations on surface acoustic wave (SAW) particle velocities, which are different from the ordinary COM equations in general use. The difference between these two sets of equations is discussed, and another type of equivalent circuit, which consists of two imaginary gyrators connected to the acoustical ports of the previously derived circuit, is derived from the ordinary COM equations. The distinctions between these two equivalent circuit models are discussed