A Metasurface-Based Low-Profile Array Decoupling Technology to Enhance Isolation in MIMO Antenna Systems

In this paper, a metasurface-based coupling reduction method is presented with the advantage of low profile for the MIMO antenna array. Unlike other metasurface-based decoupling technologies, this proposed metasurface for decoupling is loaded in the same layer as the coupled two-element patch antennas. Hence, the profile of the proposed decoupled array is greatly reduced compared to that of other published metasurface-based decoupled arrays. In this design, the two patch antennas with a short edge-to-edge distance of approximately 0.06 λ are surrounded by the period split ring resonator (SRR) elements. Next, two prototypes are fabricated; the test results show that the isolation performance for the decoupled array is better than that of a coupled array without SRRs, and the value of IS21I improves from -8 dB to -25 dB in a wide band of 5.0-6.0 GHz with IS21I <; -25 dB. The impedance matching bandwidths for two arrays without and with SRRs are approximately 700 MHz (12.7%) and 1500 MHz (27%), respectively, with IS11I <; -10 dB. In other words, a high-isolation MIMO array with the advantages of a low profile and a compact size is realized. It is exciting that the peak gains for the proposed decoupled array are improved by approximately 2 dB in the entire working band range. In addition, the efficiencies of the decoupled array increase by 15% compared to those of the coupled array, and the envelope correlation coefficient (ECC) also greatly improves. Therefore, the signs suggest that this proposed metasurface-based decoupling method is an efficient measure for MIMO array applications in the future.