Computer controlled transversal equalizer

A method of operating an equalizer network to obtain a predetermined frequency response characteristic, over a preselected frequency range, from the equalizer network in accordance with the relationship ##EQU22## the equalizer network comprising a series chain of all pass delay stages having an initial output tap connected to the input to the first stage in the chain and N additional output taps each connected to the output of a succeeding stage in the chain, N+1 scaling circuits each connected to one of the output taps, and summing circuit means for additively combining the outputs of all of the scaling circuits in the polarity relationships determined by the scaling circuits' respective scaling coefficients, the method comprising the following steps:

• a) receiving a series of M+1 attenuation numbers, H.sub.O through H.sub.M, which together represent the frequency response characteristic which is desired that the equalizer network produce;
• b) processing each of the attenuation numbers from step (a) with the Fourier function series equations ##EQU23## in which n is the number of one stage in the all pass chain, .theta. is the phase shift of any signal of frequency f within the operating range of any delay stage in the chain, and .theta..sub.m+1 and .theta..sub.m are the phase shifts for any all pass delay stage at the upper and lower frequencies, respectively, of the nominal pass band for each of the frequency control points H.sub.m, to develop a group of intermediate values b.sub.n ;
• c) additively combining the group of values calculated in step (b) in accordance with the relationships to generate a digital scaling coefficient for one scaling circuit in the equalizer network;
• ##EQU24## d) applying the digital scaling coefficient generated in step (c) to said one scaling circuit;
• and
• e) repeating steps (b) through (d) for each of the other stages of the all pass chain.