Large-Array Processing of Coherence-Degraded Signals: Analytical Study, Modeling, and Estimations of Optimization Possibilities

This paper gives a comparative analysis of various techniques of array signal processing in cases where the spatial coherence of the useful signal at the input of the receiving array is greatly weakened and the coherence length is small compared to the array size. The main focus is on realistic estimates of the practical possibilities of achieving high values of the array gain for suboptimal processing, which are close to the maximum possible values for optimal processing in such conditions. For this, a generalized parametric model of the signal coherence function is used, which permits one to analyze various reception scenarios for coherence-degraded signals and obtain key dependences characterizing output performance in terms of the array gain in a wide range of specified parameters. It is shown that the choice of the suboptimal method crucially depends on two physical parameters, namely, the relative signal coherence length (compared to the array size) and the relative level of the coherent component in the signal field (compared to its total intensity). The results are considered to be useful for various applications in long-range sonar and radar, where the coherence degradation of the signal wave fronts becomes a typical environmental effect in large array operation.