MEDIUM-LOSS SAW FILTERS WITH SYNTHESIZED CHARACTERISTICS

Medium-loss SAW filters based on the in-line dot arrray structure (similar to the 1LRAC) are reported. This configuration is very amenable to device synthesis, potentially to specifications comparable to conventional high-loss designs. The design procedure, which has been proposed in other works, fully allows for multiple reflections within the reflecting arrays and can handle chirps. The devices so far have achieved up to 0.2 dB RMS passband ripple and 32-dB rejection (after direct coupling and MSC reflection are removed). Passband loss (6-8 dB) could be reduced if transducer and multistrip coupler loss, 3 dB, can be improved. The devices also have sharp cutoffs, and fairly uniform input and output impedances in the pass and transition bands. The reflectors chosen for the reflecting arrays are thin metal dots; new data for the particular size of dots used is also presented. © 1990 IEEE