A Compact Ultralow-Profile 2-D Beam-Scanning Circularly Polarized Folded Reflectarray Employing Near-Field Phase Transformation

This letter proposes a compact ultra-low-profile 2-D beam-scanning circularly polarized folded reflectarry (CPFRA), which consists of a circular polarization selection surface (CPSS), a reflectarray (RA), and an embedded planar feed. The CPSS provides functionalities of polarization selection and beam deflection, while the RA integrates functionalities of beam focusing and beam deflection. Based on the principle of near-field phase transformation, beam-steering is achieved by rotating the CPSS and RA at different angles. Additionally, an extra phase compensation is applied to the bottom surface of the CPSS, enabling the profile of the CPFRA to be further reduced to a quarter of the focal length. The final fabricated CPFRA achieves beam-scanning in elevation angles of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\pm 40^{\circ }$</tex-math></inline-formula> and azimuth angles of 360<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^{\circ }$</tex-math></inline-formula>, respectively. Furthermore, a maximum aperture efficiency of 32.2% and a 3-dB axial ratio bandwidth of 15% are also achieved at the broadside. The proposed design exhibits a promising potential for various high-gain applications.