A two-port high-isolation MIMO antenna with hybrid semicircular–triangular radiators for sub-6 GHz and vehicular communications

This paper presents a high-isolation two-port MIMO antenna designed for sub-6 GHz wireless systems, specifically targeting the 5.75–6.05 GHz band utilized in upper sub-6 GHz spectrum, supporting applications including IEEE 802.11ax (Wi-Fi 6), emerging unlicensed/private wireless systems, and vehicular wireless communications. The antenna, realized on an FR4 substrate, integrates a semicircular–triangular hybrid radiator with slot loading to achieve effective impedance matching and enhanced bandwidth. The overall size is 90 × 42 mm² (≈ 1.72λ × 0.81λ at 5.75 GHz), supporting integration into vehicular and IoT platforms. A comprehensive design analysis is carried out using closed-form resonant frequency equations for both semicircular and triangular sections, enabling accurate prediction of operating modes. The design process is further reinforced by equivalent circuit modeling, which captures the distributed electromagnetic behavior through lumped components, validating the resonant behavior, bandwidth, and isolation. Simulated and measured results confirm excellent isolation exceeding 25 dB, stable gain of 4.65 dBi, and strong MIMO performance with ECC < 0.01, diversity gain > 9.8 dB, MEG within ± 3 dB, and CCL < 0.4 bits/s/Hz. The proposed antenna is validated using an equations-based design methodology, and robust experimental performance highlights its suitability for high-speed, low-latency wireless links in sub-6 GHz-enabled vehicular networks, smart transportation, and industrial IoT systems.