Decision feedback equalizer method and apparatus

In a decision feedback equalizer that is part of a receiver of bipolar return-to-zero (BRZ) signals, the receiver producing compensated received signals, the decision feedback equalizer having an input, an output and a memory, the input receiving the compensated received signals, the compensated received signals having a series of values X(n), where n=1, 2, 3, . . . , the output producing an output signal, the output signal having a series of corresponding output values, Y(n), the memory comprising a stored value for each possible combination of k consecutive output values, where k is a predetermined number Of preceding output values, each stored value being selectively addressable by an address value, a method for determining an output value based on a given input value, the method comprising the following steps:

• (a) receiving X(n);
• (b) forming an address value based on the k prior output values, thus, Y(n-1), . . . , Y(n-k);
• (c) retrieving a stored value based on the address value;
• (d) forming a correction factor, D(n), based on the stored value;
• (e) combining X(n) and D(n) to form an equalized received signal X'(n);
• (f) comparing X'(n) with a first predetermined value, V1, and a second predetermined value, V2;
• (g) determining Y(n) based upon the results of step (f);
• (h) determining that Y(n) equals a second symbol when X'(n).ltoreq.V2;
• (i) determining that Y(n) equals a third symbol when V2<X'(n)<V1;
• (j) comparing X'(n) with zero when V2<X'(n)<V1;
• and
• (k) replacing the stored value with the stored value plus a predetermined value, .DELTA., when X'(n)>0.