Sub-area design of a reflective metasurface for Bessel beam generation to mitigate the impact of feed occlusion

Abstract

This paper introduces a sub-area metasurface designed to mitigate the effects of feed occlusion when generating Bessel beams on reflective metasurfaces. This unit incorporates an anisotropic structure with distinct phase responses tailored for two orthogonal linearly polarized (LP) electromagnetic (EM) waves. The energy loss of the Bessel beam, situated behind the feed source, generated by the outer ring, is minimized through the superposition of the inward traveling waves and strategic partitioning of the array area. Furthermore, the principle of electric field superposition is employed to focus on the inner ring. The simulated results demonstrate that at 9 GHz, the metasurface produces a bifocal effect with focusing efficiencies of 60.1% and 64.3%, in conjunction with a Bessel beam exhibiting a diffraction-free region of 799 mm. For x polarization, the full width at half-maximum (FWHM) of the post-feed Bessel beam is 49.83 mm (1.49λ). In contrast, under y polarization, the FWHM of the Bessel beam with an off-axis angle of 30° is 47.63 mm (1.43λ). The simulated results suggest that the proposed metasurface has promising applications in point-to-multipoint or same-path multi-target wireless power transmission (WPT) systems.