Dual Circularly Polarized Folded Transmitarray in X-Band

In this article, a novel folded transmitarray (FTA) operating at X-band is developed for dual-circular-polarization (dual-CP) applications. Building upon the foundation of the previous dual linearly polarized (dual-LP) FTA design, a new dual-±45° polarized (dual-45° LP) short backfire antenna with wide bandwidth is introduced to serve as the feeding source. A novel reflective metasurface exhibiting a high polarization conversion ratio is proposed, enabling the conversion of +45° to the right-hand CP (RHCP) and −45° to the left-hand CP (LHCP), respectively. Additionally, a transmissive metasurface capable of accommodating both the x- and y-polarization facilitates phase compensation while preserving the RHCP/LHCP polarization is proposed for full-phase compensation. Additionally, the dual-CP FTA can flexibly change the beam direction by varying the phase distribution of the transmissive metasurface, and achieve any LP generation by changing the phase difference between the two excitation ports. A $29\times 29$ unit cell prototype is fabricated and experimentally verified in the anechoic chamber, with an RHCP and LHCP overlapped bandwidth covering from 8.6 to 12 GHz and 3 dB axial ratio (AR) ranges from 9.7 to 11.4 GHz. The maximum aperture efficiencies are 19.9% and 19.3%, respectively, for RHCP and LHCP radiations. This proposed dual-CP FTA has potential in satellite communication systems applications.