A high-isolation MIMO antenna design for future 5G mm-wave applications at 28 and 38 GHz

Abstract Millimeter-wave 5G communications face critical challenges including high path loss, atmospheric absorption, susceptibility to blockage, and strong mutual coupling between closely spaced antenna elements. Recent techniques such as defected ground structures, serpentine-shaped radiators, and fractal geometries have attempted to address these issues, yet many designs still suffer from narrow bandwidth, non-directional radiation patterns, or large form factors. To overcome these limitations, this paper presents a compact dual-band 2 × 2 multiple-input multiple-output (MIMO) antenna designed for millimeter-wave 5G applications at 28 GHz and 38 GHz. The proposed MIMO antenna employs a novel crescent-shaped radiating element combined with a hybrid decoupling structure integrated into a shared ground plane to achieve strong isolation between closely spaced elements. The overall MIMO antenna size is only 15.62 × 5.8 × 0.8 mm 3 , making it suitable for compact wireless devices. Full-wave simulations using two independent electromagnetic solvers (CST MWS and HFSS) confirm the reliability of the design. The MIMO antenna achieves bandwidths of 27–29.3 GHz and 35.7–40.1 GHz with peak gains of 6.48 dBi and 6.44 dBi, respectively. Excellent MIMO diversity characteristics are obtained with mutual coupling below −36 dB and −54 dB at 28 GHz and 38 GHz, respectively, and an extremely low envelope correlation coefficient below 10 −6 . In addition, the MIMO antenna demonstrates stable directional radiation patterns, high efficiency, and low channel capacity loss. These characteristics indicate that the proposed design is a promising candidate for compact millimeter-wave 5G communication systems.