Abstract This work presents the design of a compact shared radiator quad-port millimeter-wave (mmWave) MIMO antenna operating at ultrawideband frequencies ranging from 17.3 to 36.7 GHz. The proposed antenna integrates quad ports within a shared radiator created by a central circular stub extended arms as a decoupling structure, resulting in a wide impedance bandwidth, good isolation, and a low profile suitable for automotive platforms with overall dimensions of 18 × 18 × 0.5 mm 3 on RT Duroid 5880. An extended circular stub arm serves as a decoupling structure that incorporates a controlled reactive path, altering the surface current distribution, weakening near-field coupling, and increasing the effective electrical path between radiating elements. This mechanism reduces mutual coupling by forming an out-of-phase current loop with the stimulated antenna, achieving isolation better than 20 dB over the operational band. Furthermore, path loss characterization is performed under urban macrocell (UMa) and urban microcell (UMi) environments, considering line-of-sight (LoS) and nonline-of-sight (NLoS) conditions via the Alpha-Beta-Gamma (ABG) and Shooting-and-Bouncing-Ray (SBR) models. Path loss (PL) varies between 86.7 dB (UMi-LoS) and 110.3 dB (UMa-NLoS), with the SBR prediction showing better performance in NLoS due to multipath ray propagation. The incorporation of a high-isolation antenna structure with propagation modeling provides a strong framework for reliable mmWave V2V communication in a densely populated urban scenario.
Kumar et al. (Sat,) studied this question.