Mutual Coupling Reduction in Millimeter-Wave MIMO Antenna Array Using a Metamaterial Polarization-Rotator Wall

An effective technique for reducing the mutual coupling between millimeter-wave dielectric resonator antennas (DRAs) using a novel metamaterial polarization-rotator (MPR) wall is investigated and presented. The mutual coupling is reduced by embedding an MPR wall between two DRAs, which are placed in the H- plane. Using this MPR wall, the TE modes of the antennas become orthogonal, which reduces the mutual coupling between the two DRAs. The proposed MPR wall is composed of 1 x 7 unit cells along the E-plane. The mutual coupling is reduced by more than 16 dB on average (8 dB at 57 GHz, 22 dB at 60 GHz, 14 dB at 62 GHz) when the MPR wall is placed between the antennas. The proposed MPR wall nearly has no effect on the antenna characteristics in terms of input impedance and radiation pattern. The radiation pattern is almost unchanged compared to a DRA multiple-input-multiple-output (MIMO) antenna array without MPR wall. The MIMO antenna array with MPR wall is fabricated and measured. The results give a low correlation coefficient (< 0.1e-6). This is due to the fact that the MPR wall makes the two antennas orthogonal in terms of mutual coupling. The measured and simulated results show a good agreement.