Semi-symmetrical Coprime Linear Array with Reduced Mutual Coupling Effect and High Degrees of Freedom

Direction finding based on coprime array has received great interest due to the higher degrees of freedom and larger aperture size as compared with the uniform linear array.In this paper, a new semi-symmetric coprime array (SSCA) configuration is proposed to reduce the mutual coupling impact for passive sensing by exploiting the relocation of the redundant elements.First, the difference co-array of the prototype coprime array (PCA) is examined and the redundant elements are identified.Based on this examination, the second subarray (N-subarray) is split into two subarrays on opposite axes, and the zero-lag location is changed to a new location (MN+N) to construct large contiguous lags in the difference co-array.The reduction of the mutual coupling effects is tested according to the weight function of the first three lags of the SSCA array which is equal to one since there are no more redundant elements pairing in the antenna array.The closed-form expression for the hole position, the contiguous lags and unique lags are formulated and analyzed.The investigation of the SSCA is performed.The analytical expressions of the contiguous lags, unique lags, and aperture size are derived.The numerical and simulation results demonstrate that the proposed SSCA array can attain less mutual coupling leakage as compared to other array types.