Design of a Shared-Aperture Co-Polarized Antenna With Minimal Mutual Coupling for Practical Integration in a Dual-Mode OAM Array

This brief presents a co-linear polarized antenna array with low mutual coupling characteristics. The antenna element employs a hybrid feed strategy, combining probe feed with proximity-coupled feed, to excite two stacked patch radiators. The incorporation of metallic posts loading refines the configuration of the probe feed, generating the excitation of higher-order resonance mode while improving isolation between feed ports. As a result, two resonant modes (TM10 and TM $_{\text {3/2, 0}}$ ) are obtained with identical polarization and low mutual coupling of more than 20 dB. Based on the antenna element, a phased uniform circular array is constructed to generate dual-mode orbital angular momentum (OAM) waves. The array antenna is designed with appropriate OAM modes selection for further enhancement of inter-port isolation. The validity of the proposed work is confirmed through simulation and measurement. Experimental results demonstrate that the operational bands of the array antenna cover 5.04-5.14 GHz and 5.55-5.69 GHz, corresponding to OAM modes ${l}{=}0$ and −1, respectively. The port isolation is above 34 dB at these working frequencies. Additionally, the antenna boasts a low profile and facilitates easy integration with wireless devices and systems.