Transformed Nested Array Designed for DOA Estimation of Non-Circular Signals: Reduced Sum-Difference Co-Array Redundancy Perspective

In this letter, we investigate the issue of sparse array design for direction of arrival (DOA) estimation of non-circular (NC) signals, and propose the transformed nested array (TNA) which reduces overlapping virtual sensors between the difference and the sum co-array generated by the conventional nested array (NA) and can thus obtain a sum-difference co-array with higher degrees of freedom (DOFs). From the co-array redundancy perspective, we construct the TNA via two operations. The first is to exchange positions of the two subarrays of NA in order to redistribute its sum co-array to separate overlapping virtual sensors. The second is to split the dense subarray into two parts and relocate one of them aiming to further decrease redundant virtual sensors and enlarge the virtual array aperture as well. Theoretical results and numerical simulations are provided to assess the superiority of the proposed configuration.