Wideband programmable SAW filters

Programmable SAW filters represent a technology that makes use of dynamic tap weighting to enhance the capabilities of SAW devices. The prospect of tunable center frequency, selectable bandwidth, and adaptive interference suppression continue to spur interest in this technology. For the SAW IDT electrodes in our work we utilize a modified version of the two-transformer electronic circuit model (ECM) developed by Ballato for BAW devices.[1] As we previously reported [2], simulation results using the Ballato ECM are consistent with analytical results for SAW IDT radiation conductance and susceptance and overall two-port frequency response for a SAW delay line. In this paper the Ballato ECM is corroborated with experimental data for YZ-LiNbO3. Datta-Hunsinger models have been used to calculate the mechanical scattering associated with electrode arrays. Further, we offer a method for using digital filter design tools in MATLAB for synthesizing programmable SAW filters. Simulations predict, for example, that with the Kosinski filter topology [3], we can tune the frequency response from 150MHz to 250MHz for bandwidths of 10MHz. We present experimental results for a 4-tap programmable SAW filter with output tap weighting.