Wideband Co-Polarized Antenna System for In-Band Full-Duplex Applications

A wideband, mono static, co-horizontally polarized (Co-HP) antenna system with omnidirectional radiation patterns for in-band full-duplex applications is presented. The proposed antenna consists of a printed four-element dipole array and two groups of parasitic strips for impedance bandwidth and omnidirectional performance enhancement. To achieve high isolation, the four ports of the proposed antenna are excited with two orthogonal phase modes for TX and RX using a well-designed beamforming network (BFN). The BFN is a six-port microstrip circuit, which consists of two 180 degrees hybrid couplers, one 90 degrees hybrid coupler, and a Wilkinson power divider. The measured TX/RX overlapping impedance bandwidth (IMBW) of the proposed STAR antenna system is from 4.71 to 6.2 GHz, and the TX/RX isolation is more than 40 dB from 4.81 to 5.88 GHz.