Improvements to Automatic Equalizer for Data Transmission in digital telephone systems

摘要

A recursive automatic equalizer is described for implementing the telephone equalization function at a line circuit which may be multiplexed between a plurality of telephone subscriber sets. A recursive digital filter structure having programmable coefficients minimizes the error between the equalizer input and a reference signal. The recursive filter transfer function is variable via feedback coefficient update, with respect to its input and the reference signal. The recursive filter coefficients are adaptively changed to rapidly converge to a final value based upon a mean square error algorithm. The desired filter transfer function can be achieved with a low number of coefficients, for example, five, rather than the heretofore high number of coefficients required in non-recursive filter structures.