Digital convolutional filter

Abstract

A digital linear phase shift convolutional filter for filtering a series of binary number electrical signals each of which represents the magnitude of a sample of an analog electrical signal sampled at a predetermined rate. The convolutional filter utilizes a bidirectional shift register and a preferably unidirectional shift register. Each of the registers has a plurality of stages. The bidirectional shift register receives the serially presented binary number electrical signals representative of the sample magnitudes, and these samples are sequentially transferred from the output stage of the bidirectional shift register to the input stage of the unidirectional shift register. During the interval between receipt in the bidirectional shift register of binary number electrical signals representative of the sample amplitudes, the binary number electrical signals stored in the bidirectional shift register are shifted in a recirculating fashion, as are the binary number electrical signals stored in the unidirectional shift register. The binary number electrical signals appearing in particular stages of each of the registers are combined arithmetically to produce a resultant binary number electrical signal with each shift in the recirculating shift registers. These resultant signals are multiplied by constant values representing filter weights, and the products are summed to produce an output binary number electrical signal. One such output signal is produced for each new sample that enters the bidirectional shift register.