Signal flow graph analysis of transverse modes in a two-port SAW resonator

This paper shows how the spurious transverse mode response of a two-port SAW resonator can be accurately determined by the method of vector-valued Signal Flow Graph analysis. We demonstrate that the occurrence of transverse modes is primarily determined by the transversal width of the resonator´s cavity and the angle-dependent reflection factor of the grating for which we give an approximation obtained from a one-dimensional grating model. Beside the transverse mode response, this method also allows us to predict the diffraction-induced resonator loss and shift in center frequency. The measured responses of several resonators with different apertures and cavity lengths are compared with simulations. Excellent agreement between theory and experiment is obtained