Improved sidelobe performance of cosine series functions

The cosine series functions are used extensively for SAW filter design with noniterative techniques. This paper presents improved sidelobe levels of these functions by rigorous application of criteria for minimising the sidelobe peaks. An improvement of 2 dB in sidelobe levels is achieved with respect to the earlier results. A new approach is presented to determine the coefficients of these functions uniquely, which reduces the number of simultaneous equations to be solved to N-1 compared to N equations required to be solved in the earlier method.