A Dual-Polarized Linear Antenna Array With Improved Isolation Using a Slotline-Based 180° Hybrid for Full-Duplex Applications

This letter presents a simple and compact dual-polarized linear antenna array characterizing high interport isolation for in-band full-duplex communications. By using the symmetrically shared-interface configuration integrated with a 180° hybrid, the self-interference resulting from the impedance mismatching between the antenna and feeding network and the coupling among the antenna elements can be well suppressed theoretically. Furthermore, to achieve the high isolation in practice among a wide frequency band, a slotline-based 180° hybrid is proposed and studied, which features a high isolation between the sum and differential ports. For further verification, a demonstrator of a 1 × 4 array centered at 5.0 GHz is developed and fabricated. The measurements denote that the shared -10 dB impedance bandwidth of the two ports is from 4.75 to 5.18 GHz, and the interport 50 dB isolation bandwidth is from 4.55 to 5.66 GHz (over 21.7%).