Inverted-L wideband quad-port MIMO antenna with intersecting strip parasitic for 5G new radio (n77) network systems

Abstract

This research proposes a minimized-coupling and simplified inverted-L quad-port multiple-input-multiple-output (MIMO) antenna designed for 5G (n77) applications. The proposed antenna is distinguished using the characteristic mode (CM) technique, providing a unique method to analyze and optimize the antenna performance. The antenna is fabricated on a single-layer FR-4 substrate, with the upper layer consisting of a quad-port inverted-L monopole antenna and the lower layer featuring a partial ground plane. Key insights from the CM-based analysis reveal strong coupling between Ports 1&3 and 2&4, primarily driven by Modes 3 and 4. To mitigate this coupling, two pairs of intersecting strip parasitics are located at the center of the upper layer, serving as isolators. This design innovation is a key contribution of the research, offering an effective solution to enhance port isolation. Simulated models of the MIMO antenna were developed, and a prototype was fabricated and experimentally tested. The measured reflection coefficient at 3.5 GHz is 50 % (2.75–4.5 GHz), with a maximum gain of 4.5 dBi at 3 GHz. The antenna achieves port isolation greater than 15 dB, and the measured performance metrics include envelope correlation coefficient (ECC ≤ 0.05), diversity gain (DG ≥ 9.90 dB), mean effective gain (MEG ≤ -3 dB), total active reflection coefficient (TARC < -15 dB), and channel capacity loss (CCL < 0.5 dB). The novelty of this research lies in the effective use of intersecting strip parasitics to reduce coupling in the inverted-L quad-port MIMO antenna, demonstrating its potential for high-performance 5G NR (n77) applications.