CAP-3 Coprime Array for DOA Estimation With Enhanced Uniform Degrees of Freedom and Reduced Mutual Coupling

Abstract

Compared with nested array, coprime array can significantly alleviate the mutual coupling between array sensors due to the sparser array structure. However, plenty of holes in its difference co-array extremely reduce the achievable number of uniform degrees of freedom(uDOFs). In this letter, a coprime array with prime integer 3(CAP-3) is proposed, in contrast to several well-known nested arrays, which can offer comparable number of uDOFs, and alleviate mutual coupling simultaneously. Specifically, the CAP-3 consists of three appropriately placed subarrays, and it can eradicate most of the holes in difference co-array except two at both ends. Hence a large number of uDOFs can be obtained. Furthermore, CAP-3 possesses robustness against heavy level of mutual coupling due to the reduced number of sensor pairs with small inter-element spacing. Simulations reveal the advantage of the CAP-3 in uDOF, mutual coupling robustness, and direction of arrival estimation accuracy.