Grid Evolution Method for MIMO System with Unknown Mutual Coupling

Off-grid direction-of-arrival (OGDOA) methods have been widely utilized for the problem where true DOA is not on the discrete sampling grid. A novel grid evolution (GE) method is proposed to enhance resolution and reduce computational workload for off-gird methods. However, GE methods fail if unknown mutual coupling effect between antenna elements is considered. To reduce the mutual coupling effect, a grid evolution with unknown mutual coupling (GEMC) method is proposed. This approach uses expectation-maximization (EM) algorithm to estimate all unknown parameters, including mutual coupling vectors, while simultaneously making the grid evolve from coarse to dense. Compared with previous methods, this proposed method significantly reduces computational complexity and has better accuracy with unknown mutual coupling.