A Broadband High Efficiency Spin-Decoupled Folded Transmitarray Antenna with Independent Beam Control

High-gain circularly polarized folded transmitarray antennas have garnered increasing attention due to their notable advantages. Nonetheless, previous studies predominantly focused on generating a single circularly polarized high-gain beam. The concurrent and autonomous generation and manipulation of left-hand circularly polarized (LHCP) and right-hand circularly polarized (RHCP) beams, i.e., spin angular momentum (SAM) decoupling, has consistently captivated the interest of researchers. This communication presents a high-gain SAM-decoupled folded transmitarray antenna, distinguished by its broadband width, high efficiency, and low-profile design, while successfully achieving independent regulation of LHCP and RHCP beams. To assess the effectiveness of this design, a SDFTA prototype was fabricated and measured, and the results are shown in reasonable agreement with the simulation. The measured results reveal that the gain variation less than 3 dB relative bandwidth is superior to 21.8% and 22.4% for LHCP and RHCP beams, respectively. The 3 dB axial ratio bandwidth also encompasses 21.9% and 30.4% for LHCP and RHCP beams, respectively. The peak aperture efficiency for the LHCP beam attains 26.9%, and likewise, the peak aperture efficiency for the RHCP beam attains 20.9%. It is paramount to underscore that our design marks an innovative departure from the earlier constraint that FTAs or FRAs could only generate and control a single circularly polarized beam in a single band.