DECISION FEEDBACK EQUALIZER WITH A PATTERN DETECTOR

摘要

A decision feedback equalizer has an adaptive filter responsive to a demodulated data sequence and a residual intersymbol interference (ISI) signal for estimating ISI which occurs during pulse transmission of a period of T seconds and producing an estimated ISI signal. A subtractor subtracts the estimated ISI signal from a received signal which involves an ISI signal to produce a residual signal. A circuit is provided for extracting the residual ISI signal from the residual signal and a delayed residual signal which is produced by delaying the residual signal. A demodulator produces the demodulated data sequence from the residual signal and applies the data sequence to the filter. A pattern detector detects a particular consecutive pattern out of the demodulated data sequence. The residual ISI signal is applied to the filter in response to an output of the pattern detector. The invention dispenses with the need for an automatic gain control circuit, thereby permitting scaling down the hardware.