Simplifications for analysis of SAW multipole resonators

This paper presents a simplified analysis for the passband of a SAW filter. The filter has the form of a 1-track two-port resonator, consisting of two transducers in the cavity formed by two reflecting gratings. This arrangement can give a low-loss, low-ripple multipole response. It is shown here that the grating reflection coefficient can be taken to be constant in the passband, leading to an analytic result for the device insertion loss and simple expressions for the passband ripple. The paper also considers a 2-track resonator consisting of two 1-track resonators connected in parallel. This can be arranged to give no direct coupling between the input and output transducers, thus increasing the stop-band rejection. It also gives simpler expressions for the passband response. Expressions for the ripple lead to simple criteria for the design of low-ripple devices