Sidelobe cancellation technique for achieving high rejection in SAW filters

A new technique called sidelobe cancellation technique (SCT) to achieve high stopband rejection in SAW filters is described, for varying requirements of shape factor and sidelobe levels, by using an eigen function approach. Cosine series functions with improved sidelobe levels are employed. Each design is characterized by the order of the cosine series and the number of functions used to obtain a particular shape factor and rejection. Limited trimming of shape factor also can be achieved in each design. The filters described here are compared with the Kaiser window filter and are found to be efficient. Measured response of a prototype SAW filter using the approach given in this paper is plotted, and it is in good agreement with the simulated response.