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

High-gain circularly polarized (CP) folded transmitarray antennas (FTAs) have garnered increasing attention due to their notable advantages. Nonetheless, previous studies predominantly focused on generating a single CP high-gain beam. The concurrent and autonomous generation and manipulation of left-hand CP (LHCP) and right-hand CP (RHCP) beams, i.e., spin angular momentum (SAM) decoupling, has consistently captivated the interest of researchers. This communication presents a high-gain SAM-decoupled FTA, 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, an 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 CP beam in a single band.