16-Channel Surface-Acoustic-Wave Filter Bank.

摘要

A 16-channel surface-acoustic-wave filter bank has been fabricated on a single 8.7 sq cm y-cut LiNbO3 substrate using reflection gratings as filtering elements. The bi-directional z-directed acoustic signal propagates through a sequence of ion-beam etched gratings each with a different period. Each grating resonantly reflects at 90 deg a narrow frequency band to an x-directed output transducer. This configuration yields an efficient filter bank in which the minimum unmatched insertion loss to any one channel is -30 dB, + or - 1/2 dB, and in which spurious signals due to triple transit and bulk waves are reduced below -80 dB with respect to the input. Each grating is depth weighted according to a Hamming function for sidelobe suppression to -37 dB below the peak signal in each pass channel. Each channel has a 6 dB passband of 2 MHz. The channels are 2 MHz apart and range from 200-230 MHz. Reactive energy storage within gratings introduce deviations from ideal filter performance. A method which compensates for these effects is described. (Author)