US 4,539,690 A · Automatic and adaptive digital nonlinear decision feedback equalizer

Abstract

A method and apparatus for equalizing a scanned noisy digital signal with an automatic and adaptive decision feedback equalizer comprising a nonrecursive part and a recursive part. A switch is disposed in the feedback loop of the equalizer between a decision device and the recursive part of the equalizer for allowing the determination of a step size factor. For this purpose the switch is in such a position that a reference signal can be fed into the feedback loop and at the same time the gradient coefficients are fed to a device for setting the filter coefficients. The gradient coefficients are determined at that point in time where the switch was set to the other switch setting. The number of the required interation intervals to approaching the minimum of the equalization error can be decreased by employing the method of the present invention. In addition, the filter configuration can be employed in a multiplex operation.

Claims27

Dependent claims

An automatic and adaptive digital nonlinear decision feedback equalizer comprising

an input provision for entering signals;
a digital filter having a recursive part and a non-recursive part and connected to the input provision and generating an auxiliary signal (w.sub.n);
a threshold decision device connected to the output of the digital filter for determining if the value at the input of the threshold decision device is coordinated to a certain signal level region;
a switch having a first input connected to the output of the threshold decision device and having its output connected to a recursive input of the digital filter;
and
a reference signal source connected to a second alternate input of the switch for inducing in its switched on position in the digital filter a reference signal (r.sub.n) for, in conjunction with the auxiliary signal, the determination of a step factor for the recursion process.

3 more elements

A method for equalizing an incoming noisy signal employing an automatic and adaptive decision feedback equalizer comprising

feeding back the output signal from an in part nonrecursive and in part recursive digital filter;
feeding the output signal of the filter to a threshold decision device for determining if the value at the input of the threshold decision device is coordinated to a certain signal level region;
providing a reference signal from a reference signal source;
connecting a first input terminal of a switch to the output of the threshold decision device, where the output terminal of the switch is connected to the filter, for allowing the filter to generate an equalizer output;
connecting a first input terminal of a switch to the output of the decision device, where the output terminal of the switch is connected to the filter, for allowing the filter to generate an equalizer output;
connecting a second input terminal of the switch to the reference signal source for allowing the filter to generate a filter output signal;
and
employing the filter output signal to determine the step factor for the filter.

5 more elements

A system for equalizing an incoming noisy digital signal for an automatic and adaptive decision feedback equalizer where a correction criterion is derived from a reference signal and from a filter output signal and where the correction criterion is minimized by way of iteration according to a gradient procedure, wherein the equalizer comprises a recursive and a nonrecursive part, where a switch is disposed in a feedback loop between a threshold decision device (D) for determining if the value at the input of the threshold decision device is coordinated to a certain signal level region and the recursive part, where in a first position (1) of the switch (Sl) an equalizer output signal (y.sup.n) and where in a second position (2) of the switch (S1) a reference signal (r.sub.n) is fed to the feedback branch of the filter and where the reference signal (r.sub.n) is employed together with the filter output signal (w.sub.n) for the determination of the step factor for the recursion process.

Dependencies are inferred from the claim text.

Automatic and adaptive digital nonlinear decision feedback equalizer

Life of this patent

Automatic and adaptive digital nonlinear decision feedback equalizer

Life of this patent

Abstract

Claims27