AbstractThe coupled‐mode theory is extremely useful for analysis of such periodic structures as grating reflector, resonator, and unidirectional transducer making use of electrode reflection as important constituent elements for the SAW devices. Here, the coupled‐mode equations describing the transduction characteristics of the inter‐digital electrode transducer (IDT) are derived directly by the perturbation theory. In addition, the parameters for the coupled‐mode equations are presented for quartz, LiTaO3 and LiNbO3 substrates.Next, based on the coupled‐mode equations, the relationship among the quantities of the electrical port and two acoustic ports of the IDT is derived. The entire periodic structure was represented by a simple distributed equivalent circuit. The equivalent circuit analysis method is described for the analysis of the device characteristics. To show the usefulness of the present method, a backward‐wave type trapped‐energy SAW resonator and the resonator coupled filter are analyzed.