Apparatus and method for wide bandwidth adaptive filtering

摘要

Method and apparatus for adaptive filtering a first signal to produce a second signal that approximates a desired signal including an acoustic charge transport type programmable transversal filter (PTF) having a number of taps where each tap corresponds to an associated delayed first signal and each tap having means for providing a variable tap weight to modify the filter response. The first signal is coupled to the PTF and the output of the PTF produces the second signal. A summer compares the output of the PTF and the desired signal to produce an error signal. A programmable delay line has time delays programmable to integer multiples of the PTF tap spacing to provide a delayed version of the first signal, and a multiplier multiplies the error signal and the delayed input of the programmable delay line to produce a gradient signal. The gradient signal is filtered with an analog lowpass filter to produce a filtered gradient signal which in turn is converted to a digital signal by a low bandwidth analog to digital converter. A microprocessor implements a filtered gradient algorithm to update the PTF filter tap, load the new tap weight into the PTF, and reconfigure the programmable delay line to produce a filtered gradient for another tap. The comparison of the PTF output with the desired signal continues to develop an error signal and the adaptive process is repeated until the error signal becomes substantially zero which results in the second signal more closely approximating the desired signal.