Broadband Reflector Antenna With High Isolation Feed for Full-Duplex Applications

A broadband circularly polarized reflector antenna with high isolation between transmitter and receiver channels is demonstrated theoretically and experimentally. The proposed antenna achieves |S11|21 dBic (with a maximum value of 28 dBic) over the 4-8 GHz operating frequency range. A dual-polarized coaxial cavity antenna is designed to serve as the feed for the axis-symmetry reflector antenna. The inner conductor of the coaxial cavity antenna is extended to integrate the feed with the reflector; therefore, avoiding the use of mounting struts. The proposed configuration is used to realize an antenna subsystem for monostatic simultaneous transmit and receive (STAR)/full-duplex applications. The monostatic STAR operation is achieved by the use of a simple, low-loss beamformer network where hybrids and circulators are arranged to cancel any signal leakage from transmitting to receiving paths leading to high isolation. Practically, the proposed system achieves measured isolation >30 dB which is bounded by the amplitude and phase imbalances of the deployed commercial off-the-shelf components.