Direction Of Arrival Estimation In Mutual Coupling Scenarios

Direction-of-arrival(DOA)estimation is an important branch in the field of array signal processing.It refers to the processing of the signals received by the antenna array by using statistical signal processing technology and various optimization methods to estimate the DOA of the incoming signals.It has a wide range of applications such as radar,sonar,navigation and wireless communications.The high resolution of subspace based methods relies on the accurate structure of the steering vectors,hence,this kind of methods is sensitive to array bias.In real applications,because of the nonideal environment or the devices,the manifold of the array deviates from the real one,resulting in deterioration of estimation performance.This paper mainly studies the DOA estimation algorithm in the case of mutual coupling.Firstly,the basic model of array direction finding is introduced,including uniform linear array and nonuniform linear array.Then,the properties and structure of mutual coupling matrix are introduced,and the effect of mutual coupling on DOA estimation is analyzed by comparing the case of mutual coupling with the ideal case.In uniform linear array,in the case where mutual coupling and non-uniform noise coexist,a DOA estimation algorithm based on covariance fitting creterion is proposed.The algorithm uses the structure of mutual coupling matrix and selection matrix to construct a new manifold matrix.DOA estimation problem is then transformed into an semidefinite programming problem,and the power of non-uniform noise can be obtained.Simulation results show that the algorithm can distinguish the incoming signals when the incident angle is close.Under the conditions of small number of snapshots and coherent signals,the algorithm can achieve higher resolution.For DOA estimation of nested arrays with mutual coupling,this paper proposes an algorithm to estimate the angle accurately after estimating the mutual coupling coefficient.The algorithm mainly uses the sparse subarray of the nested array which is not affected by the mutual coupling effect.We then obtain the coarse DOA estimates by comparing the estimates of the two subarrays of the nested array.On this basis,the mutual coupling coefficients and accurate DOA estimation can be finally retrieved.Simulation results show that compared to the uniform linear array with the same number of antennas,the proposed algorithm has better estimation performance due to the extended array aperture.