Apodized single-phase unidirectional transducer SAW devices

Single-phase unidirectional transducer (SPUDT) filters have been shown to have the advantage of producing low insertion loss, but yet to be simple to manufacture at a relatively low cost. However, the synthesis of SPUDT devices has always been relatively difficult, especially with regard to deriving an optimized transduction and reflection apodization function. A technique for using both overlap and withdrawal weighting for SPUDT filters to realize a specific filter response is presented. Experimental SPUDT filters with insertion losses as low as 4.8 dB and with a sidelobe rejection of greater than 50 dB for various fractional bandwidths on various piezoelectric substrates are presented. The experimental responses of these apodized devices are compared with the theoretical simulated response. The application of these low-loss devices for use with surface-mount packaging is also demonstrated