Programmable transversal filter

Abstract

A programmable transversal filter (10) utilizes a plurality of programmable multiplying means (M.sub.1 -M.sub.4). The result of each multiplication is summed by a summing circuit (7), thus providing an output signal (y(t)). The delay network of this invention comprises a plurality of sample and hold circuits (S.sub.1 -S.sub.4) which are selectively connected to the input bus in sequence, in order that one sample and hold circuit may store an analog signal sampled during the present time instant, with other sample and hold circuits storing a plurality of analog signals each of which has been sampled during a corresponding one of a plurality of preceding sample periods. An analog cross-point switch (51) is utilized wherein each of said plurality of time delayed analog signals may be selectively applied to a selected multiplying means. By utilizing an analog cross-point switch, a transversal filter having programmable tap weights is constructed wherein the tap weights remain fixed in the multipliers until reprogrammed, without the need for rotating the tap weights among the plurality of multipliers. Furthermore, each input voltage sample is stored in a single sample and hold circuit. Because the transversal filter of this invention does not cycle the tap weights among multipliers, the dynamic range of the output signal of the transversal filter constructed in accordance with this invention is increased over that of prior art programmable transversal filters, with a substantial decrease in fixed pattern noise.