Mutual coupling exploitation for point-to-point MIMO by constructive interference

In this paper, we propose a joint analog-digital (A/D) beamforming scheme for the point-to-point (P2P) multiple-input-multiple-output (MIMO) systems, where we exploit the mutual coupling effect to further improve the system performance. By judiciously selecting the value of each load impedance for the antenna array, it will be shown that the mutual coupling effect can be beneficial. We firstly prove that the full elimination of mutual coupling is not achievable solely by changing the values of each load impedance. We further propose a joint A/D technique where the resulting interference aligns constructively to the useful signal vector with the concept of constructive interference. Numerical results show that the proposed schemes can achieve an improved performance compared to systems with fixed mutual coupling, especially when the antenna spacing is small.