US 8,477,890 B2Granted

Geometric detector for communicating through constant modulus (CM) interferers

AssigneeBAE Systems Information and Electronic Systems Integration Inc.

InventorsLee M. Garth, Gary R. Lomp, Matthew J. Sherman

Life of this patent

Estimating the term…

Loading patent…

Abstract

A desired signal modulated with N symbols is detected in the presence of a constant modulus (CM) interferer that produces M symbols. Observation samples corresponding to the desired signal and the interferer are obtained from a signal recovery stage. N observation constellations are defined, each having M constellation points corresponding to the symbols produced by the interferer, and the points form a circular perimeter of the constellation with a radius corresponding to the strength of the interferer. The perimeter of each constellation is centered on one of N defined symbol points representing the different possible symbols of the desired signal. Distances between the observation samples and the circular perimeter of each observation constellation are determined. For each observation sample, the symbol point on which the constellation perimeter closest to the sample is centered, is selected as a symbol of the desired signal.

Claims23

Dependent claims

A method of detecting a desired signal by a radio or receiver in a communications system, wherein the desired signal is modulated to obtain N possible symbols and is received in the presence of a constant modulus (CM) interferer that produces M possible symbols, including the steps of:

obtaining observation samples from a signal recovery stage in the receiver, the samples corresponding to the desired signal and the interferer as received simultaneously at the receiver;
defining N symbol points each corresponding to one of the N possible symbols modulated on the desired signal;
defining N observation constellations each having M constellation points corresponding to the M possible symbols produced by the interferer;
defining a circular observation perimeter for each observation constellation, wherein the perimeter includes the M constellation points of the constellation and has a radius corresponding to the strength of the interferer;
centering the observation perimeter of each of the N observation constellations on a corresponding one of the N defined symbol points;
for a given observation sample obtained from the signal recovery stage, determining on which observation perimeter lies a point that is nearest to the given observation sample;
and
selecting, for the given observation sample, the symbol point about which the determined observation perimeter is centered as a symbol of the desired signal.

5 more elements

A communications receiver, comprising:

a signal recovery stage constructed and arranged to produce successive composite observation samples each corresponding to a desired communications signal and a constant modulus (CM) interferer as received simultaneously at the receiver, wherein the desired signals are modulated to obtain N possible symbols, and the CM interferer produces M possible symbols;
and
a signal detection stage coupled to the recovery stage and including one or more signal processing stages configured and operative to:
(a) define N symbol points each corresponding to one of the N possible symbols modulated on the desired signal;
(b) define N observation constellations each having M constellation points corresponding to the M possible symbols produced by the interferer, the constellation points of each observation constellation defining a circular observation perimeter, wherein the perimeter includes the M constellation points of the constellation and has a radius corresponding to the strength of the interferer;
(c) center the observation perimeter each of the N observation constellations on a corresponding one of the N defined symbol points;
(d) for a given observation sample obtained from the signal recovery stage, determine on which observation perimeter lies a point that is nearest to the given observation sample;
and
(e) select, for the given observation sample, the symbol point about which the determined observation perimeter is centered as a symbol of the desired signal.

6 more elements

Dependencies are inferred from the claim text.