A SAW filter bank using hyperbolically tapered transducers

Abstract

It is shown that the hyperbolically tapered transducer is capable of launching a relatively narrow SAW (surface acoustic wave) beam from some point across a wide transducer aperture. The center of this narrow SAW beam varies linearly with frequency across the transducer. Thus, the transducer performs the spatial frequency sorting as it launches a wave. This makes it an ideal candidate for a filter bank or frequency-division multiplexer. A 14-channel multiplexer has been developed with a total bandwidth of 120 MHz centered at 180 MHz, (1 octave) out-of-band rejection of 40 dB and an insertion loss of 19 dB. Cascading filters demonstrates an out-of-band rejection of over 80 dB with an insertion loss around 30 dB.<>