US 5,202,903 A · Noise-immune space diversity receiver

Abstract

In a space diversity receiver, matched filters and a like number of channel estimators are respectively coupled to diversity antennas to receive sequentially coded symbol sequences. A branch metric calculator receives the outputs of the matched filters and the estimates from the channel estimators to calculate a branch metric of the received sequences for coupling to a maximum likelihood (ML) estimator. The branch metric is obtained by summing branch metric coefficients derived from channel estimates respectively with the output of the matched filters or by summing branch metric coefficients derived from a vector sum of channel estimates with the matched filter outputs. In another embodiment, adaptive channel estimators are provided for deriving channel estimates from received sequences and the output of an ML estimator. First branch metrics are derived from the received sequences and supplied to a branch metric quality estimator in which quality estimates of the channels are derived from the first branch metrics. An evaluation circuit evaluates the first branch metrics according to the quality estimates and produces a second branch metric for coupling to the ML estimator.

Claims12

Dependent claims

A diversity receiver having a plurality of diversity antennas for simultaneously receiving sequentially coded symbol sequences transmitted over distinct communications channels from a point of transmission to said antennas, comprising:

a plurality of channel estimators respectively coupled to said diversity antennas for deriving estimates of impulse responses of said communication channels respectively from coded symbol sequences received by said antennas;
a plurality of matched filters associated respectively with said channel estimators and said diversity antennas, each of said matched filters having a tapped delay line coupled to the associated antenna and a plurality of multipliers coupled respectively to successive taps of said tapped delay line for controlling tap weight coefficients of said multipliers in response to an output signal from the associated channel estimator and integrating weighted signals generated by said multipliers to produce a matched filter output;
a branch metric calculator for receiving the outputs of said matched filters and said estimates from said channel estimators for calculating a branch metric of the signals received by the antennas;
and
a maximum likelihood sequence estimator coupled to said branch metric calculator.

2 more elements

An adaptive diversity receiver having a plurality of diversity antennas for simultaneously receiving signals over distinct communications channels from a point of transmission to said antennas, comprising:

a plurality of adaptive channel estimators respectively coupled to said diversity antennas for deriving estimates of impulse responses of said communication channels respectively from signals received by said antennas and a previously received signal;
a plurality of branch metric calculators coupled respectively to said diversity antennas for deriving first branch metrics respectively from said signals respectively received by said antennas;
a branch metric quality estimator coupled to said adaptive channel estimators for deriving from output signals of said channel estimators a plurality of branch metric quality estimates of said communications channels, respectively;
a branch metric evaluation circuit coupled to said branch metric calculators and said branch metric quality estimators for evaluating said first branch metrics in accordance with said branch metric quality estimates and producing a second branch metric;
and
a maximum likelihood sequence estimator for deriving a maximum likelihood estimate of said received signals from said second branch metric and applying said maximum likelihood estimate to said adaptive channel estimators as said previously received signal.

3 more elements

Dependencies are inferred from the claim text.

Noise-immune space diversity receiver

Life of this patent

Noise-immune space diversity receiver

Life of this patent

Abstract

Claims12