Doubly apodized SAW filters

The design of a surface acoustic wave filter having two apodized in-line transducers is presented. The positions and weights of the taps in both transducers are obtained simultaneously by considering the finger-by-finger interaction between the two transducers. Two design optimization criteria are compared. A device consisting of two 21-tap transducers with a 10 MHz passband centred at 50 MHz is built on 128/spl deg/ rotated Y-cut LiNbO/sub 3/ to verify the design. We show that the sidelobe suppression is limited by diffraction, which was not included in the design procedure. The response is compared to that obtained by a singly-apodized SAW filter of comparable length designed with the Remez exchange algorithm.