Hole-free sparse array for highly efficient direction of arrival estimation: Enhanced uniform difference co-array

Sparse arrays with OoNTHORN sensors can offer O (N-2). number of degrees of freedom by exploiting the difference co-array that can be obtained from the second-order statistics of received signals. In this article, a novel sparse array with seven subarrays (SA-7S) by carefully assembling the subarrays is proposed, and the resulting SA-7S can generate a hole-free uniform difference co-array. The sensor locations of the SA-7S array are uniquely determined by a closed-form expression and the number of achievable degrees of freedom is analytically presented as well. Theoretical analysis shows that the SA-7S can provide a higher number of degrees of freedom than most sparse linear arrays. Simulations are performed to validate the advantage of the proposed array in terms of uDOFs, mutual coupling and direction of arrival estimation performance.