Acoustic surface wave band filters with weighted fan transducers

A method for improving the performance of SAW filters is proposed which is based on shaping the frequency-response characteristics of a filter assumed to consist of two identical fan transducers. The shaping method involves the reduction of the sidelobe height of the elementary frequency-response characteristic in order to attenuate the sidelobes in the amplitude-frequency (AF) response characteristic of the filter. The sidelobes of the elementary characteristics are attenuated by using fewer electrodes in one of the transducers. The AF filter characteristics produced using ordinary fan transducers are compared with those obtained using transducers which shape the characteristics in accordance with the proposed principle. It is concluded that the proposed method shows promise for improving SAW-filter performance.