A Colinearly Polarized Full-Duplex Antenna With Extremely High Tx–Rx Isolation

In this letter, we present a colinearly polarized in-band full-duplex (FD) microstrip antenna system with passive self-interference cancelation achieved from extremely high interport isolation. The proposed FD antenna achieves this isolation enhancement without the use of any circulator, hybrid or complex feed-network, by adopting a novel combination of: 1) field-confinement near individual antennas due to metallic vias, and 2) U-shaped slots etched from the ground plane. The proposed FD antenna demonstrates interport isolation values of
$>\!\!54$
dB over the operating band of 5850–5945 MHz (IEEE 802.11p band for V2X-ITS) and
$\approx \!\!90$
dB at 5.9 GHz, along with broadside gain of 5.63 dBi and X-pol level less than 20 dB. The design procedure of the proposed planar FD antenna is explained and verified by CST-MWS full-wave simulations along with experimental results on fabricated antenna prototype.