US 6,307,884 B1 · Dual decision feedback equalizer with selective attenuation to improve channel performance

Abstract

An apparatus and method for improving error rate performance in a communication channel utilizes a dual decision feedback equalizer (DDFE) through the application of selective attenuation. An improved DDFE comprises first and second decision feedback equalizers (DFEs) operably connected in parallel to receive a series of input signals zk. The DFEs independently generate two series of decisions ;1k and ;2k in relation to peak magnitudes of the series of transmitted signals zk by filtering the series of decisions ;1k and ;2k to generate filtered outputs (a*p)1k and (a*p)2k based on previous decisions, and summing the filtered outputs (a*p)1k and (a*p)2k with the transmitted input series zk to generate two series of decision variables ã1k and ã2k, to remove effects of intersymbol interference. The improved DDFE further comprises first and second attenuation blocks, so that when a mismatch is detected between the series of decisions ;1k and ;2k, a selective attenuation gain less than one is introduced into each feedback filter loop. This results in a reallocation of some of the decision energy associated with the correct series of decisions to the erroneous series and helps the erroneous DFE to make correct decisions sooner, thereby improving the error rate performance of the channel.

Claims11

Dependent claims

In a communication channel of the type characterized as having a dual decision feedback equalizer comprising a pair of nominally independent decision feedback equalizers operably coupled in parallel to receive a series of input signals, each decision feedback equalizer comprising a slicer which applies a selected threshold to generate a series of decisions nominally indicative of peak data values of the series of input signals and a feedback filter having a response excited by previous decisions which provides a filtered output which is subtracted from the series of input signals in order to cancel intersymbol interference and generate a series of decision variables which are input to the corresponding slicer, each slicer further generating a series of error terms in relation to presence of noise in the channel as a difference between the corresponding series of decision variables and series of decisions, the improvement comprising:

a pair of attenuators, each associated with a different one of the decision feedback equalizers and applying an attenuation gain of less than one to the associated feedback filter when a mismatch occurs between the series of decisions output by the decision feedback equalizers.

An improved dual decision feedback equalizer which applies a selective attenuation to improve error rate performance, comprising:

a first decision feedback equalizer operably coupled to receive a series of input signals zk and comprising:
a first slicer which utilizes a selected threshold −α to generate a series of decisions ;1k nominally indicative of corresponding peak data values of the series of input signals zk;
a first feedback filter, operably coupled to receive the series of decisions ;1k from the first slicer, which provides a filtered output (a*p)1k based on previous decisions;
and
a first summing junction, operably coupled to receive and sum the filtered output (a*p)1k from the first feedback filter and the series of input signals zk to generate a series of decision variables ã1k which are input to the first slicer;
a second decision feedback equalizer operably coupled in parallel with the first decision feedback equalizer to receive the series of input signals zk and comprising:
a second slicer which utilizes a selected threshold α to generate a series of decisions ;2k nominally indicative of corresponding peak data values of the series of input signals zk;
a second feedback filter, operably coupled to receive the series of decisions ;2k from the second slicer, which provides a filtered output (a*p)2k based on previous decisions;
and
a second summing junction, operably coupled to receive and sum the filtered output (a*p)2k from the second feedback filter and the series of input signals zk to generate a series of decision variables ã2k which are input to the second slicer;
and
first and second attenuators, operably coupled to the first and second slicers, respectively, which apply the selective attenuation to the first and second feedback filters, respectively, when a mismatch is detected between the series of decisions ;1k and ;2k.

9 more elements

Dependencies are inferred from the claim text.

Dual decision feedback equalizer with selective attenuation to improve channel performance

Life of this patent

Dual decision feedback equalizer with selective attenuation to improve channel performance

Life of this patent

Abstract

Claims11