Design of low-shape-factor SAW filters having a single acoustic track

The problem discussed here is a realization of frequency responses both with a shape factor of 1.3 or less and with a stopband rejection of 40 dB or more for the most simple and compact configuration of surface acoustic wave (SAW) filters. This SAW filter modification has one acoustic track and only two selective elements: an input apodized interdigital transducer (IDT) and an output withdrawal weighted one. The majority of known algorithms for optimization of withdrawal weighted (WW) IDTs are effective for transducers with a large number of electrodes and band width of 1% or less. An algorithm proposed here is intended for optimization of broadband WW transducers. Experimental characteristics of designed filters are: a bandwidth of 5-9%, a stopband rejection of 115-55 dB, a 3 dB-10 dB shape factor of 1.07-1.3.