Electromagnetic coupling shielding in compact MIMO antenna using symmetric T-shaped metamaterial structure for 5G communications

In this paper, a new symmetric metamaterial (MM) based T-shaped shield is proposed to enhance isolation between antenna elements in a two-antenna multiple-input-multiple-output (MIMO) system useful for 5G wireless communications. The proposed antenna is designed with two adjacent H-plane coupled dumbbell-shaped slotted rectangular patches and parasitic stubs with a small center-to-center gap of 0.39 lambda(min) at 4.5 GHz. The antenna is developed using FR-4 epoxy low-cost substrate with a compact size of 0.45 lambda(min) x 0.75 lambda(min) x 0.048 lambda(min) to cover the 5G n79 band of 4.5-5.01 GHz (10.73%). The T-shaped MM shield is comprised of a hanging hook shape unique symmetric resonator with near-zero permeability, epsilon negative (ENG), and negative refractive index (NRI) properties, which shows excellent band-stop characteristics within the antenna bandwidth. The designed T-shaped shield is employed in the middle of the two MIMO antennas, enhancing isolation to > 28.5 dB by greatly suppressing the near-field mutual coupling energy. Moreover, the antenna impedance bandwidth is improved by 3.95% and the envelope correlation coefficient (ECC) is reduced from 0.003 to 0.0006 (0.02 to 0.01 for radiation) within the desired band, confirming high isolation and excellent channel capacity. Furthermore, an outstanding diversity gain (DG) > 9.99 dB and low channel capacity loss (CCL) < 0.3 bits/s/Hz are achieved by the proposed MM shielding. The effectiveness of the proposed MM shielding technique is verified by the measurement of the MIMO prototype and shows promising performance for 5G MIMO applications.