Enhanced DOA Estimation With Augmented CADiS by Exploiting Array Motion Strategies

With its increased aperture and enlarged minimum spacing among sensors, coprime array with displaced subarrays (CADiS) receives a great deal of attention among sparse arrays. However, the holes in the difference co-array of CADiS extremely degrade the achievable number of uniform degrees of freedom (uDOFs). In recent years, increasing researches of direction of arrival (DOA) estimation with moving sparse arrays have brought new insights into the releasing the holes problem. In this paper, we first explore the structure of difference co-array generated from array motion, and propose a hole-free motion strategy that can fill all the holes in difference co-array of coprime arrays, and resulting increased number of uDOFs as well as array aperture. Secondly, based on the analysis of hole positions, we propose another motion strategy that needs only one step motion of CADiS to generate a difference co-array with no holes in the central part. We find all the qualified steps length of the one-step motion method and provide the closed-form expression of the corresponding achievable number of uDOFs. Finally, the number of uDOF and DOA estimation accuracy of the proposed motion strategies are compared with several state-of-the-art motion methods. Numerical results show the superiority of the proposed methods.