Decision feedback equalizer for canceling short-and long-multipath

Abstract

In a decision feedback equalizer, transmitted signals are received by an array of antennas and baseband symbols are recovered. A forward filter provides weighting of the recovered baseband symbols with first coefficients so that precursor multipath components of a transmitted symbol are canceled and combines the weighted symbols. A set of first delay elements provide respective delays to one of the baseband symbols to produce a short- and a long-delayed baseband symbol. A set of correlators is provided for detecting correlations between the baseband symbol and the short- and long-delayed baseband symbols. A set of second delay elements provide respective delays to a decision symbol to produce a short- and a long-delayed decision symbol. A selector is responsive to a correlation detected by one of the correlators for selecting one of the short- and long-delayed decision symbols. A feedback filter shifts the selected decision symbol along a tapped-delay line to produce successively shifted decision symbols, multiplies them with second coefficients and combines the multiplied decision symbols to produce an output signal that cancels postcursor multipath components of the transmitted symbol. The output signals of the forward and feedback filters are combined to produce a pre-decision symbol which is used by a decision circuit to produce a decision output for coupling to the second delay elements as the aforesaid decision symbol.