Scanning Quasi-Nondiffractive Beam Enabled by Low-Profile Source-Integrated Launcher Based on Metasurface

In this article, a highly integrated transmission-type approach is proposed to generate scanning quasi-nondiffractive beams using a source-integrated folded transmitarray antenna (FTA) based on metasurface (MS). The proposed approach achieves large-angle scanning of quasi-nondiffractive beams in two dimensions while significantly reducing the profile height of the launcher, which effectively mitigates the lack of compactness and integration in existing research approaches. As a validation, a circularly polarized (CP) scanning quasi-nondiffractive beam launcher in the Ku-band is designed, which consists of two rotatable chiral MSs and a planar patch feed integrated into the bottom reflector. The MSs are designed to provide perfect polarization selectivity for folding the beam propagation path, alongside accurately implementing the required phase shifting. The two nonlinear phase profiles with controllable depth of field and the spherical wave compensation of the integrated feed source are encoded onto the two MSs. The designed launcher with a profile as low as$2.5\lambda _{0}$was modeled and fabricated. Dynamic scanning of quasi-nondiffractive beams, covering a 104° field of view (FoV) and 360° azimuth within a specified depth-of-field area, can be achieved by rotating the two MSs simply. Good agreement between simulation and measurement results proves the effectiveness of the proposed strategy. The proposed launcher has great potential for near-field high-speed communication, wireless energy transfer (WET), and detection applications, especially in space-constrained situations.