Distributed source processing with linear nested arrays

We consider the problem of using linear nested arrays to estimate the direction of arrival (DOA) of spatially distributed sources and detect the source number, where we have more sources than the actual physical sensors. Angular spread, caused by the multipath nature of distributed sources, makes the commonly used point source assumption ineffective. In this paper, we establish the signal model for distributed sources using a nested array. Due to the characteristics of distributed sources, the regular spatial smoothing technique, which is used to exploit the increased degrees of freedom provided by the co-array, no longer works. We thus propose a novel spatial smoothing approach to circumvent this problem. Based on the analytical results, we construct corresponding DOA estimation and source number detection methods. The effectiveness of the proposed methods is verified through numerical examples.