DIGITAL AUTOMATIC LINE EQUALIZER WITH MEANS FOR CONTROLLING TAP GAINS OF TRANSVERSAL FILTER ON MEAN POWER OF OUTPUT FROM THE FILTER

摘要

A digital automatic line equalizer for compensating distortion of a digital signal transmitted through a transmission line comprises a transversal filter (11) having a set of tap gains for producing an equalized signal as a filter output from the digital signal incoming thereto. A first multiplier (200) squares a current one of the filter output to produce a squared signal and other multipliers (201-20 l ) multiplies the current and the previous ones of the filter output to produce product signals. A calculator (21) calculates from the squared signal and the product signals a mean value of sum of the squared signal and weighed product signals for a predetermined time duration. A controller (15) determines a set of values from the mean value to make the set of tap gains equal to the set of values thereby to maintain the mean value to a predetermined value as a reference value so that the transversal filter (11) produces the equalized signal. The calculator (21) may comprise a plurality of weighing circuits (22) for producing the weighed product signals, an adder (25) for producing the sum, and an averager (26) for producing the mean value. A controller (15) may comprise a comparator (27) for comparing the mean value and the reference value to produce an error signal, a memory (30) for storing a plurality of sets of values for the set of tap gains, and a selection controller (29) for selecting one of the plurality of set of values in response to the error signal.