A Low-Profile Risley-Prism-Based 2-D Beam-Scanning Circularly Polarized Folded Transmitarray Antenna at Ku-Band

In this communication, a novel folded transmitarray antenna (FTA) based on the principle of the Risley-Prisms antenna is proposed, which can achieve circular polarized (CP) beam scanning in both azimuth and elevation planes with low scanning loss. The antenna consists of a CP patch feed source, a metal ground plate, and two rotatable circular polarization selective metasurfaces (CPSMs). The CPSM can fully reflect the CP incident waves in one mode (left-hand CP (LHCP) mode or right-hand CP (RHCP) mode) and transmit the CP incident waves in the other mode. By mechanically rotating two CPSMs above the feed source, the beam's scan range covers 0(?)-52(?) in the elevation plane and 0(?)-360(?) in the azimuth plane. The measured maximum gain is 22.9 dBic at 16 GHz, with a total efficiency of 30.1%. Moreover, since the wave's propagation path is folded, the overall profile of the proposed antenna is only 1.92 ?(0) including the feed source. The proposed antenna has the advantages of low profile, compact structure, low loss, low cost, high gain, and easy fabrication. It has potential in applications that have limited space and weight, such as satellite communication and vehicle communication systems.