TO-ANA: An Augmented Nested Array for Third-Order Cumulant-Based DOA Estimation

To overcome the uniform degrees of freedom (uDOFs) limitation of conventional sparse arrays based on second-order statistics, third-order cumulant (TOC) have recently been introduced into sparse array design for direction-of-arrival (DOA) estimation. To further improve the achievable uDOFs of TOC-based sparse arrays, this letter proposes a third-order augmented nested array (TO-ANA) by shifting the nested array, introducing an augmented subarray, and finally employing a partial sensor mirror-flipping strategy. In this letter, closed-form expressions for the sensor locations and achievable uDOFs are derived, and the optimal array parameters are analytically determined. Numerical results demonstrate that, compared with existing third-order sparse arrays, the proposed TO-ANA achieves higher uDOFs and lower mutual coupling (MC) effect, thereby improving DOA estimation performance.