An Improved Unfolded Co-Prime Linear Array Design: No Ambiguity Problem for DOA Estimation

In this paper, an improved ambiguity-free direction of arrival (DOA) estimation method with unfolded coprime linear array is proposed. In the case of ambiguity elimination problem, the existing stacking subarray-based method can suppress the ambiguity problem. However, for the two subarrays, when there are two DOAs which have the same steering vector with a given DOA, ambiguity problem still occurs. To solve this problem, a decision variable was defined and a modified method based classic beamforming technique was proposed, which can eliminate the ambiguity problem. However, this method needs additional algorithm to distinguish the true DOAs besides multiple signal classification (MUSIC) spectrum. So we design an improved ambiguity-free array, where there are three coprime integers. By moving the reference element, the linear combination relation of the steering vectors can be broken. In this way, MUSIC algorithm can be applied directly and no additional algorithm needs. Compared to the original method, the proposed method can solve the ambiguity problem effectively and efficiently. Numerical simulations are given to demonstrate the effectiveness and superiority of the proposed method.