This paper proposes a quad-port dual-band multiple-input-multiple-output (MIMO) antenna that operates at the n78 band (3.5 GHz) and the dedicated short-range communications band (5.9 GHz), addressing the requirements of emerging 5G and vehicle-to-everything (V2X) communication systems. The presented MIMO antenna employs multi-stub radiating structures with a defected ground configuration using planar, non-resonant geometries without vias and multilayer stacking to achieve compact footprint of 0.95λg × 0.95λg, improved impedance matching and enhanced bandwidth without integrating substrate integrated waveguide cavities, complementary split ring resonators and neutralization line techniques. The fabricated antenna prototype offers measured impedance bandwidths of 680 MHz and 670 MHz at both operating bands, with mutual coupling less than −20 dB. The antenna has a gain of 3.6 dBi at 3.5 GHz and 4.7 dBi at 5.9 GHz, while maintaining an efficiency of more than 83% and an omnidirectional radiation pattern suitable for vehicular integration. MIMO diversity analysis shows an envelope correlation coefficient < 0.03, diversity gain ≈ 9.99 dB, total active reflection coefficient < -10 dB, and channel capacity loss ≈ 0.1 bps/Hz, indicating excellent diversity and isolation performance. Furthermore, the antenna performance is validated on the issue of housing effect and the vehicle installation environment, whereby roof top integration increases the directivity while maintaining the omnidirectional coverage, demonstrating that it is suitable for reliable, high data rate 5G-enabled V2X communication.
Arumugam et al. (2026) studied this question.