Highly Isolated Copolarized Microstrip Full-Duplex Antenna by Surface-Waves Suppression

This letter introduces a novel two-layer substrate approach aimed at enhancing the isolation between two closely packed antennas. The method involves mitigating the surface waves by integrating two decoupling lines between the substrates. Decoupling scheme synthesis is explained based on variation in common and differential mode impedances. Furthermore, a reduction in the surface waves is achieved by creating a slot in the ground plane. A fabricated prototype of the proposed structure exhibits 40 dB isolation within the 5.78 GHz to 5.98 GHz band, with maximum isolation of up to 70 dB at 5.92 GHz. The proposed structure is simple, cost-effective, and has good radiation patterns, which make it a good candidate for 5G/6G full-duplex applications.