Improvement in Isolation Between MIMO Antennas Using MTM Stop-Band Cells in the mm-Wave Band

In our work, an efficient method to minimize the mutual coupling (MC) from two symmetrical rectangle antennas (Ra) functioning at 26 GHz band is described. This is achieved by adding an arrangement of three split-ring resonator (SRR) cells (placed in the Y-plane) between 2-element MIMO antennas that are positioned in the X-plane. The SRR design is intended to provide bandstop functionality within the antenna bandwidth. As a result, the mutual coupling level is reduced by 23 dB while maintaining the antenna's performance and by packing the MIMO structure with three cells of SRR. In addition, the prototype antenna's simulated isolation varies from -32 to -55 dB on the frequency band of 25.5-26.6 GHz. The reflection coefficient is roughly -40 dB at 26 GHz, with a high gain of 7.5 dB and efficiency higher than 90%. This makes our antenna an effective competitor for MIMO applications at the 26 GHz band enabling the fifth generation (5G) cellular communications.