Equalizer adaptation

A method of equalizing a received data signal comprising a series of bits, the method comprising:

• forming an adjusted bit signal for a bit based on a signal received for a relevant bit period and at least one weighted contribution from another bit period;
• comparing the value of the adjusted bit signal to a slice threshold to determine a of the adjusted bit;
• categorizing the adjusted bit as a hard bit if the adjusted bit has a signal value above an upper threshold or below a lower threshold and otherwise as a soft bit, wherein the upper threshold is above the slice threshold and the low threshold is below the slice threshold, and
• adjusting the weighting for said at least one weighted contribution from another bit period;
• wherein a first adjustment to the weighting is made if the adjusted bit signal is categorized as a soft bit and a second, different adjustment is made if the adjusted bit signal is categorized as a hard bit;
• increasing the upper threshold by a first amount if the adjusted bit signal is above the upper threshold;
• decreasing the upper threshold by a second amount if the adjusted bit signal is between the upper threshold and the slice threshold;
• increasing the lower threshold by said second amount if the adjusted bit signal is between the slice threshold and the lower threshold;
• and
• decreasing the lower threshold by said first amount if the adjusted bit signal is below the lower threshold;
• wherein said first amount has a magnitude of k*D and wherein the second amount has a magnitude of (1−k)*D where k is a proportion of soft bits desired in the received data and D is a constant.

An equalizer comprising;

• a combination module for forming an adjusted bit signal based on a signal received for a relevant bit and at least one weighted contribution from another bit;
• and
• control logic configured to:
• compare the value of the adjusted bit signal to a slice threshold to determine the polarity of the adjusted bit;
• categorizing the adjusted bit as a hard bit if the adjusted bit has a signal value above an upper threshold or below a lower threshold and otherwise as a soft bit, wherein the upper threshold is above the slice threshold and the low threshold is below the slice threshold, and
• adjust the weighting for said at least one weighted contribution from another bit;
• wherein a first adjustment to the weighting is made if the adjusted bit is a soft bit and a second, different adjustment is made if the adjusted bit is a hard bit;
• wherein said first adjustment comprises increasing the weighting of the contribution from the another bit period for which the polarity of the relevant bit is determined to match the polarity of the adjusted bit signal and decreasing the weighting of the contribution from the another bit period for which the polarity of the relevant bit is determined to be opposite to the polarity of the adjusted bit signal;
• and
• wherein said second adjustment comprises decreasing the weighting of the contribution from the another bit period for which the polarity of the relevant bit is determined to match the polarity of the adjusted bit signal and increasing the weighting of the contribution from the another bit period for which the polarity of the relevant bit is determined to be opposite to the polarity of the adjusted bit signal.