A Quad Port MIMO Antenna Designed with an X-Shaped Decoupling Structure for Wideband Millimeter-Wave (mm-Wave) 5G FR2 New Radio (N258/N261) Bands Applications

This article presents a newly developed quad port-MIMO antenna, showcasing notable advancements in performance and an extensive impedance bandwidth. The antenna design is founded on a symmetrical configuration, incorporating an X-shaped decoupling structure, alongside employing the multi-slit and multi-slot techniques. These enhancements culminate in a compact, low-profile antenna measuring 40 × 40 × 0.8 mm, while maintaining a remarkable wideband capability. For experimental purposes, the proposed antenna is fabricated using Roger RT/Duroid 5880 with a dielectric constant of 2.2 and a thickness of 0.8 mm. Our investigations reveal that the antenna's impedance bandwidth spans from 22.5 to 29.2 GHz (bandwidth of 6.7 GHz), ensuring isolation levels surpassing −27 dB. The designed MIMO antenna offers an envelope correlation coefficient of 0.004, a diversity gain of 10.0 dB and a peak gain of 4.25 dB. Remarkably, this antenna successfully balances wide bandwidth, compact dimensions, outstanding isolation and superior MIMO diversity metrics. These qualities make it a desirable choice for 5G new radio bands N258 (24.25–27.5 GHz) and N261 (27.5–28.35 GHz) applications.