Four-Port MIMO Antenna System with Enhanced Bandwidth for 5G mm-Wave Applications

This study introduces an innovative MIMO antenna tailored for 5G millimeter-wave applications. By integrating a rectangular closed loop (RCL) and split-ring resonators (SRRs) with a monopole structure, the design achieves notable enhancement in impedance performance around the 26.5 GHz frequency. The MIMO configuration comprises four radiating elements positioned on a common PCB with a space-efficient footprint of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\mathbf{3 0} \times \mathbf{3 0} \mathbf{~ m m}^{\mathbf{2}}$</tex>. The developed four-port antenna system offers a wide impedance bandwidth of 2 GHz (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$25.7-27.7 \text{GHz}$</tex>) centred at 26.5 GHz, achieving a total efficiency of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$85-95 \%$</tex> over the operating band. Additionally, the antenna exhibits envelope correlation coefficient (ECC) values within acceptable limits, ensuring excellent isolation between the ports. The antenna achieves an average gain of 7 dBi, confirming its effectiveness for deployment in millimeter-wave 5G New Radio (NR) bands n257, n258, and n261.