Wideband Gain Enhancement of High-Isolation Fabry–Pérot Antenna Array With Tandem Circular Parasitic Patches and Radial Gradient PRS

A high-isolation Fabry–Pérot (FP) antenna array with wide bandwidth and high gain is proposed for Ku-band vehicle satellite communications. Each antenna element consists of a pair of tandem circular parasitic patches (TCPPs), a radial gradient partially reflective surface (PRS), and a reflector, respectively, separated from the ground plane with a double-dumbbell-shaped slot (DDSS) by air layer and foam dielectric. The slot radiator steers the TCPPs to create multiple resonant frequencies and then the impedance bandwidth is widened. The impedance matching could be improved by adjusting four circular slot diameters of the DDSS. The gain is raised by TCPPs and radial gradient PRS, which function to guide the electromagnetic field and uniformize the aperture near-field, successively. The reflector with several resonator elements is used to reduce the backside radiation. As proof of concept, the FP antenna array prototype with a height of $0.613\lambda _{0}$ has been fabricated and measurements confirming simulations are provided. Experimental results show that the impedance bandwidth ranges from 13.48 to 16.95 GHz [22.8% fractional bandwidth (FBW)], and the realized gain is up to 21.59 dBi. A decoupling metallic strip could achieve over 40.8 dB isolation. The proposed antenna element is easily extended for the multiple-input multiple-output (MIMO) and beamforming antennas, further improving the directivity.