Analysis and Design of an Ultrawideband Dual-Polarized Antenna for IBFD Applications

This communication investigates design requirements for a class of dual-polarized in-band full-duplex (IBFD) antennas utilizing a symmetry of structures and a differential-feeding scheme. The analysis reveals that, to achieve zero coupling between two ports, the out-of-phase power divider (PD) does not need to have perfect isolation and perfect matching at the two output ports. A more relaxed set of requirements for the PD is derived for the first time. Based on this, an ultra-wideband cross-shaped Vivaldi antenna is designed for IBFD applications with very high isolation. The measured 10 dB return loss bandwidth is 1.26–8.0 GHz (145.5%), while the measured port-to-port isolation is >42 dB at 1.26–4.7 GHz (115.4%) and >34 dB within the whole operational bandwidth.