Nonhomogeneity detection method and apparatus for improved adaptive signal processing

DETAILED DESCRIPTION Briefly stated, the present invention discloses apparatus and method for improving detection of targets in a radar system that employs adaptive filtering.
A nonhomogeneity detector eliminates nonhomogeneous signals from the population of signals received.
An adaptive filter weight controller estimates covariance matrices from only homogenous signals.
Thus the apparatus and method improves the probability of detecting the presence or absence of a target at the same time that it decreases the probability of a false alarm by improving the performance of an adaptive filter.
The present invention dramatically improves the performance of adaptive filtering in nonhomogeneous environments by detecting and excluding nonhomogeneous auxiliary signals from estimation of covariance and from adjustment of adaptive filter weights.
Specifically, the present invention adds signal processing units that enhance current airborne radar adaptive filtering techniques in nonhomogeneous environments.
The added signal processing units of the present invention provide the capacity to automatically: (1) analyze the covariance structure of auxiliary signals; (2) detect nonhomogeneous auxiliary cells; (3) exclude cells detected as nonhomogeneous from the estimate of interference covariance and the adjustment of adaptive filter weights.
The improvement in adaptive filtering of the present invention yields increased SINR, thereby making more probable the detection of weak targets at a lower rate of false alarms.
Analysis of measured multichannel airborne radar data demonstrates a dramatic improvement in adaptive filter performance from the present invention.
A nonhomogeneity detector and an auxiliary signal selector comprise the signal processing units added by the present invention.
They overcome the deleterious effects of nonhomogeneous interference on adaptive filtering, thereby overcoming the drawbacks of current approaches to airborne adaptive filtering, as the latter assume the signal environment to be homogeneous in all cases