Underdetermined DOA estimation with unknown source number in nonuniform noise

We present a new direction-of-arrival (DOA) estimator for nested arrays, which does not require source number knowledge and works in the presence of nonuniform noise. We first give the number of unique elements and the number of elements which appear more than once in the difference coarray obtained from the nested arrays. Then we construct 2N — 5 Toeplitz matrices based on the elements appearing more than once. Finally, we introduce a method for DOA estimation which does not require the source number information. Numerical examples are provided to demonstrate the effectiveness of the proposed algorithm.