High Isolation H-Plane Placed Metasurface MIMO Antenna Using Characteristic Field Cancellation

A simple and effective isolation enhancement method for the H-plane coupled metasurface (MTS) antenna is proposed for the fifth-generation (5G) indoor access point application. First, the characteristic mode analysis (CMA) is conducted on two extremely closely placed MTSs to find out two pairs of desired resonant modes. Second, a via group is introduced to control the modal electric-field (E-field) cancellation degree at the unexcited antenna. The initial location of the decoupling vias is given by studying the superposed E-field variation. Benefiting from the stable distribution of the mode electric field around the resonant frequency, a high isolation level is achieved in a wide bandwidth. A slot-coupled feeding configuration is designed to validate the decoupling concept and a maximum isolation improvement of 27.4 dB is achieved. Finally, an experimental four-port multiple-input multiple-output (MIMO) antenna array is designed, and an isolation of better than 40 dB within 3.3–4.2 GHz is achieved. The proposed via-loading decoupling method based on CMA has promising prospects for massive MIMO applications.