A Risley-Prism-Based Dual-Circularly-Polarized Symmetric Dual-Beam Folded Reflectarray Antenna With Beam Scanning Capability

This paper proposes a low-profile Risley-prism-based dual-circularly-polarized symmetric dualbeam folded reflectarray antenna (FRA). This FRA generates two circularly polarized (CP) beams, one lefthand CP (LHCP) and the other right-hand CP (RHCP), to perform beam scanning at opposite elevation angles within the same azimuth plane. Specifically, the proposed FRA consists of Transmittarray#1 (TA#1), Transmittarray#2 (TA#2), a polarization conversion reflection metasurface (PCRM), and a feed antenna. Initially, the x-polarized spherical electromagnetic wave emitted by the feed is converted into a y-polarized plane wave at the PCRM. Subsequently, the y-polarized wave is decomposed into RHCP and LHCP waves at TA#2. Finally, the two CP beams are transformed into orthogonal polarizations and undergo beam deflection again at TA#1. By rotating the metasurface and the feed antenna based on the Risley prism principle, the two CP beams can achieve ±40° elevation scanning in any azimuth plane. The folded design of the electromagnetic wave propagation path reduces the antenna's profile, resulting in a profile height to-diameter ratio of only 0.35. The measured results show that the maximum realized gains for the RHCP and LHCP beams in the broadside state are 20.28 dBic and 19.03 dBic, corresponding to aperture efficiencies of 22.96% and 17.22%, respectively. Featuring a low profile and low cost, this antenna is highly suitable for applications such as satellite detection.