A compact quad-port dielectric resonator MIMO antenna with intrinsic isolation for sub-6 GHz 5G network

This paper presents the systematic design, fabrication, and experimental validation of a compact quad-port dielectric resonator antenna (DRA)-based MIMO system for sub-6 GHz 5G applications. An aperture-fed excitation combined with optimized spatial arrangement is employed to achieve high inter-port isolation intrinsically, without using additional parasitic decoupling networks or external isolation elements. Each radiating element supports dual-mode operation by exciting a fundamental linearly polarized TE₁₁δ mode at 3.5 GHz and a higher-order TE₁₂δ mode at 3.9 GHz, enabling dual-band performance. The proposed four-port MIMO antenna achieves inter-port isolation exceeding 20 dB at the operating frequencies of 3.5 GHz and 3.9 GHz within a compact footprint of 0.35λ₀ × 0.35λ₀. Experimental results demonstrate excellent diversity characteristics with ECC below 0.05, CCL of approximately 0.1 bps/Hz, peak gain up to 2.62 dBi, and radiation efficiency approaching 89%. The moderate gain level is well suited for compact user terminals, indoor access points, and small-cell 5G devices, where omnidirectional coverage and low correlation are prioritized over high directional gain. The close agreement between simulated and measured results confirms the robustness of the design, making it a promising candidate for compact sub-6 GHz 5G communication devices.