AUTOMATIC EQUALIZER FOR COMMUNICATION CHANNELS

Delay equalization for phase-modulated data transmission by communication channels is automatically provided by selection of the least amplitude-modulated output of a plurality of delay equalizers, each having a frequency-independent amplitude characteristic and a different complementary, freqency-dependent delay characteristic over the frequency passband of the channels. Envelope detectors determine the extent of amplitude modulation present in each output of a set of delay equalizers and the detected amplitude modulation is compared in binary decision circuits to select an equalizer output having the least amplitude modulation. Plural stages of detection and comparison are provided for 2n delay equalizers where n>1, and automatic equalizers are cascaded for extended complementary matching o channel delay distortion over the frequency passband.