On Compact Folded Reflectarray With Reduced Profile and Improved Aperture Efficiency

This letter presents a folded reflectarray (FRA) antenna that employs an upper phase-compensating linear polarization selection surface (LPSS) and a lower polarization-twisting and phase-compensating reflectarray (RA) to achieve a high-efficiency beam focusing with a reduced profile. A magneto-electric (ME) dipole feed, integrated within the lower RA, enables a compact and fully planar configuration. Different to traditional grid polarizers adopted in FRAs only for polarization selection, the LPSS proposed in this work features additional functionality of phase compensation, so that the profile can be further reduced to one third rather than one half of the focal length as that of conventional FRAs. Furthermore, when compared with folded transmitarrays (FTAs) which also typically have a profile of one third of the focal length, the LPSS would not suffer inevitable losses of the transmission elements in FTAs, therefore leading to an improved aperture efficiency. Measurements show that the proposed FRA achieves a maximum aperture efficiency of 46.2% and a 3-dB gain bandwidth of 22%. These promising characteristics alone with its reduced profile make it very suitable for a wide range of high-gain applications.