COM analysis of SAW waveguide-coupled resonator filters
Abstract
A new method of analyzing surface acoustic wave waveguide-coupled (WGC) resonator filters using the coupling-of-modes (COM) technique is presented. General COM equations for the coupled transducers and coupled reflectors are derived. The mechanism of coupling is described by using the coupling of waves in the opposite directions within one track and the coupling of waves in the same direction between two adjacent tracks. The reflection, transduction, attenuation and coupling between two tracks are included in the model. Closed-form solutions for the case of uniform coupled transducers and coupled gratings are obtained. A model based on the above analysis is developed for two-pole WGC resonator filters, and Y-parameters are obtained from this model. Computed results are shown to agree with experimental work.