The effect of spatial averaging on spatial correlation matrices in the presence of coherent signals
Darel A. Linebarger, D.H. Johnson · IEEE Transactions on Acoustics Speech and Signal Processing · 1990
Two types of spatial averaging are considered: subaperture averaging and redundancy averaging. The reduction of coherence due to subaperture averaging is shown to depend on the separation between the sources: highly coherent, closely spaced sources remain highly coherent after subaperture averaging. In finite averaging situations, this remaining high degree of coherence will prevent adaptive direction-finding methods such as MUSIC or EV from resolving the two signals. In contrast, redundancy averaging greatly reduces intersignal coherence regardless of source spacing, but bias may be introduced into the source bearing estimates.>