A UNIFIED APPROACH TO COHERENT SOURCE DECORRELATION BY AUTOCORRELATION MATRIX SMOOTHING

A wide variety of techniques have been developed to deal with coherent signals at a sensor array. Many of these techniques have the structure of a pre-processor followed by a standard adaptive beamforming or angle of arrival estimation algorithm, The pre-processor is designed to reduce the cross-correlations between the arriving signals. A general decorrelation technique of this type called autocorrelation matrix smoothing (AMS) is described in this paper. The processing in AMS consists of a two-dimensional linear filtering operation on the correlation matrix of the array measurements, A number of the previously proposed decorrelation techniques can be interpreted as special cases of AMS, corresponding to different choices for the mask used to filter the correlation matrix. Although the previous methods were not originally formulated in terms of AMS, the unified interpretation points out relations between the techniques and suggests improved techniques. This paper summarizes the basic properties of AMS, explains the unified interpretation of previous decorrelation methods, and describes some extensions for improved decorrelation.