An Unambiguous Hole-Filling method for Large-Baseline Distributed Nested Arrays Using Auxiliary Array

Distributed nested arrays with large baseline can significantly enhance array aperture with only a few elements. However, such spacing often results in increased sidelobe levels and angular ambiguities. To address these issues and achieve ambiguity-free DOA estimation, this paper proposes a subspace algorithm based on inserting contiguous auxiliary arrays. When the distributed nested array structure is set, we analyze the symmetric hole range, and derive a closed-form solution for both the required minimum number of auxiliary elements and the optimal position where to insert the first auxiliary element. This strategy ensures complete coverage of the hole region and maintains the continuity of the differential virtual array. Numerical simulations demonstrate that the proposed algorithm effectively removes angular ambiguities and outperforms the conventional dual-scale ESPRIT approach, achieving estimation accuracy comparable to that of a ULA with an equivalent aperture while using fewer elements.