An Ultralow-Profile Beam-Scanning Circularly Polarized Folded Transmitarray

An ultralow-profile beam-scanning circularly polarized (CP) folded transmitarray (FTA) is proposed in this letter. The antenna comprises two upper circular polarization multifunction metasurfaces (CPMMs) and a bottom reflectarray integrated with a planar CP patch feed. Based on Risley prism principle, two-dimensional (2-D) beam-scanning is achieved by mechanically rotating two CPMMs. In addition, by introducing additional phase modulation on the bottom reflectarray, the FTA profile is reduced to one fifth of the focal length, resulting in an ultralow-profile configuration. An antenna prototype is designed and fabricated to validate the design methodology. The experiment results show that the antenna can achieve a satisfactory 2-D beam scanning performance, with a scanning range of ±41° in the elevation plane and 0-360° in the azimuth plane, respectively. Furthermore, during the beam scanning, a maximum aperture efficiency of 32.6%, a gain variation less than 2.2 dB, and an axial ratio less than 3 dB, are realized. These appealing characteristics make the proposed antenna a good candidate for various high-gain applications such as satellite communications.