Wideband frequency domain adaptive filter module

A new realisation of adaptive filter is reported which employs a cascade of forward and inverse surface acoustic wave (SAW) analogue Fourier transform processors interconnected via a digital interface. The interface multiplies the transformed input by a set of weights stored in RAM and compares the products against a separately supplied desired complex spectrum. The resulting error is used to update the RAM weights via a feedback loop. The use of frequency domain processing in the adaptive filter offers faster convergence than conventional time domain adaptive transversal filters, and the incorporation of SAW chirp transform techniques extends the adaptive filter to MHz's of signal bandwidth.