Optimization of broadband uniform beam profile interdigital transducers weighted by assignment of electrode polarities.

This paper considers techniques for optimizing surface acoustic wave (SAW) interdigital transducers (IDTs) with uniform electrode length (no apodization). Unlike other optimization techniques developed for this type of IDT, the algorithms proposed here choose the best electrode structure on the basis of how well it meets the specifications, not in the time domain, but in the frequency domain directly. In the first step of the optimization, a periodic transducer is synthesized. The weighting technique for providing a desired frequency response involves assigning polarities to the individual electrodes. The next step of the IDT selectivity improvement is the optimization of the electrode positions. In addition, the second algorithm can synthesize specified nonsymmetric frequency responses. A set of IDTs and SAW filters with bandwidths of 1 to 14% has been designed using this algorithm.