A Novel Third-Order Nested Array for DOA Estimation With Increased Degrees of Freedom

In this work, a novel third-order nested array is proposed for direction-of-arrival (DOA) estimation, which achieves significantly more degrees of freedom (DOF) than the existing third-order and second-order nested arrays. It is known that for the DOA estimation with a third-order nested array, we can utilize the uniform lags of the third-order coarray (TOCA) of the array. In the proposed array, the elements are placed strategically so that the TOCA attains significant uniform lags. We provide the closed-form element locations of the proposed third-order nested array with the mathematical expression of the uniform lags of the TOCA. The proposed third-order nested array also suffers from significantly less mutual coupling as a framework is devised to place the elements in appropriate locations so that the mutual coupling will be substantially less. The required simulations are performed to show the advantages of the proposed third-order nested array over the existing third-order and second-order nested arrays.