Shifted super transformed nested array for DOA estimation of non-circular signals with increased uDOFs and reduced mutual coupling

In this work, a scheme for array structure design is proposed to maximize uniform degrees of freedom (uDOFs) and reduce mutual coupling. It starts by exchanging the positions of two subarrays within the nested array, followed by mitigating mutual coupling through sensor relocation due to the dense subarray, and ultimately increasing uDOFs by globally shifting the entire array to the right. Following this scheme, the concept of Shifted Super Transformed Nested Array (SSTNA) is introduced and general guidelines for the construction of SSTNA are provided. Analytical expressions for the continuous region of the virtual apertures and uDOFs are derived. Furthermore, the optimal shifting parameter and the first three weight functions are determined for SSTNA. Theoretical analysis shows that SSTNA can effectively reduce mutual coupling while maintaining high uDOFs. In strong mutual coupling scenarios, simulation results are provided to demonstrate the effectiveness and superiority of the proposed design.