Patent ID: 8576903

Claim:
A multi-level pulse amplitude modulation (PAM-N) decision feedback equalizer (DFE), comprising: a coefficient computation unit for setting feedback coefficients of the DFE; and a feedback unit configured to mitigate, using the feedback coefficients, effects of interference from data symbols that are adjacent in time to an input PAM-N data symbol; an error-and-decision unit comprises a number of N of adders, wherein each of the N adders subtracts the pseudo equalized input PAM-N data symbol from one of the plurality of decision levels generated by the calibration unit to produce a number of N error values, a number of N−1 comparators coupled to the N adders, wherein each of the N−1 comparators generates a decision used to determine the least error value out of all the computed error values, a decoder for recovering the data based on the error values and for generating a selection signal, and a multiplexer coupled to the N adders and the decoder, the multiplexer outputs the least error out of the computed error values based on the selection signal, wherein the error-and-decision unit is configured to compute a least error value respective to one of a plurality of decision levels and to recover the data modulated in the input PAM-4 data symbol, wherein the least error value indicates a difference of a pseudo equalized input PAM-N data symbol from an optimal position of the one of the plurality of decision levels, wherein the one of the plurality of decision levels corresponds to a modulation level used to modulate data in the input PAM-N data symbol; and a calibration unit for adaptively setting the plurality of decision levels based, in part, on the least error value, thereby enabling for compensating for gain changes resulted by a cable on which the input PAM-N data symbol is received and further compensating for embedded offsets of the error-and-decision unit.