US 5,513,216 A · Hybrid equalizer arrangement for use in data communications equipment

Abstract

A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). The hybrid DFE structure is designed so that one form of tap values dominates over the other. This allows only the dominate tap values to be used by the transmitter during precoding and reduces the transmitter complexity. In particular, a hybrid DFE is designed so that the I(z) coefficient values dominate over the N(z) coefficient values, where the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively. A respective Tomlinson precoding scheme in the transmitter uses only the I(z) values. Since only the I(z) values are used in the precoder of the transmitter, the NP-DFE of the receiver is kept active during the communications phase. Conveniently, the continued use of the NP-DFE in the receiver allows the receiver to track small changes in the channel.

Claims10

Dependent claims

A hybrid decision feedback apparatus for use in data communications equipment, the apparatus comprising:

an adaptive feedforward filter for removing a first portion of intersymbol interference from a received signal to provide a first signal;
wherein the adaptive feedforward filter section includes a number of pre-cursor taps and a number of post-cursor taps, where the number of pre-cursor taps is more than the number of post-curser taps;
an intersymbol interference decision feedback filter for removing a second portion of intersymbol interference from the first signal;
and
a noise predictive decision feedback filter for removing a portion of channel noise from the first signal:
wherein the intersymbol interference decision feedback means and the noise predictive decision feedback are responsive to at least one control signal to separately adapt during a training interval:
and
wherein during the training interval the intersymbol interference decision feedback means adapts to the first signal before the noise predictive decision feedback means.

5 more elements

Dependencies are inferred from the claim text.

Hybrid equalizer arrangement for use in data communications equipment

Life of this patent

Hybrid equalizer arrangement for use in data communications equipment

Life of this patent

Abstract

Claims10