A Low-Profile Circularly Polarized OAM Beam-Scanning Folded Transmitarray Antenna Based on Risley Prism

In this paper, a Risley-prism-based low-profile circularly polarized beam scanning folded transmitarray antenna (FTA) is proposed. The scanning beam of the proposed FTA can carry orbital angular momentum (OAM). The antenna consists of two circularly polarized rotatable transmission metasurfaces (CPRTMs), a high-gain feed antenna, and a metal plate. Specifically, by rotating the two CPRTMs, 0-45° elevation scanning can be achieved in any azimuth plane. Due to the vortex phase being added to the upper CPRTM, the FTA can generate the l=+1 mode OAM beam while realizing beam scanning. Simulated results show that the antenna can achieve a maximum gain of 18.2 dBic at 10 GHz for l=+1 mode. This FTA features a low profile and high gain, and it holds great application value in miniaturized OAM wireless communication systems.