Modelling of SAW transversely coupled resonator filters using coupling-of-modes modeling technique

A modeling method is described for using coupling-of-modes to model each transverse mode of a surface acoustic wave (SAW) transversely coupled resonator filter (TCF). Closed-form expressions are obtained which accurately describe the characteristics of this device class. The derivation of the model is described, a comparison between theory and experimental device performance is given, and the use of the model to synthesize optimized SAW TCFs is illustrated. The model is compared to experimental results in which excellent agreement is obtained over a 60- to 80-dB range, depending upon the device design. The accuracy of the model combined with closed-form expressions for filter performance allows for the use of nonlinear least-squares fitting techniques for experimentally determining coupling-of-modes (COM) model parameter values