Decision feedback adaptive equalizer acting on zero states following a non-zero state

摘要

In an adaptive equalizer of the decision feedback type for reducing intersymbol interference in subsriber loops of a telephone system, the corrected digital signal is applied to means (80) for detecting the occurrence in the signal of a zero state following a non-zero state. When that occurs, a correlator (26, 126; 28, 128; 30, 130) samples the signal during the "zero" bit period and applies the sample to an integrator (50, 150; 60, 160; 76, 176). The integrator output varies the coefficients of the feedback signal applied to the input means (10) for addition to the incoming digital signal (S) to provide the corrected signal (Sn). The equalizer may have several stages (A, B, C), each for detecting a "zero" state in a different bit period following the original pulse. Also the circuitry may be duplicated for each polarity if the input signal is bipolar.