1. A digital filter for a series of samples of a signal, said filter characterized in that it includes: an input to which the samples of the signal to be filtered are applied; an input control means for separating said samples into data blocks of a fixed length; at least two different circular convolution generators, each having an input receiving each of said data blocks and generating the terms resulting from the circular convolution of the samples of each said block with an associated block of coefficients defining the required filtering operation of the generator; a product means for each circular convolution generator for multiplying the output of the associated one of said generators by a correcting term specific to the attached generator; an adder for adding together the corresponding terms in the outputs of said two product means; and a means for combining selected ones of the terms supplied by said adder to produce a series of samples representing the filtered signal.