Improved Design of Single-Phase Unidirectional Transducers for Low-Loss SAW Filters

Abstract

This paper describes several new designs based on the SPUDT (single-phase unidirectional transdu cer) concept. In order to improve on the sidelobe suppression performance of previous SPUDT designs, a new structure with withdrawal weighted IDT's and intra-transducer reflector strips is presented. An aperture weighting technique for SPUDT's is also described for > 35 dB sidelobe suppression. A stepped-electrode SPUDT for enhanced 5th harmonic low-loss operation is also detailed. In addition, a slanted SPUDT arrangement is described for mid-loss (>5 dB, <10 dB) filters with up to 10% bandwidths.