SAW programmable notch filters for adaptive interference suppression

The authors report a novel SAW (surface acoustic wave) programmable filter that uses Sezawa waves on a monolithic metal-ZnO-SiO/sub 2/-Si structure for adaptive interference suppression. The operation of the device is similar to that of those using Fourier transform schemes, except that the frequency separation is performed spatially. The programmability and the spectrum monitoring are performed by means of an acoustoelectric effect. The authors demonstrate a bandpass and a band-reject response of the filter with a center frequency of 213 MHz, bandwidth of approximately=26 MHz, insertion loss of approximately=27 dB, and out-of-band rejection of approximately=35 dB. Programmable notch-filter behavior is demonstrated in a direct-sequence spread-spectrum receiver to suppress a single-tone interfering signal.<
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