Loading Metalens: An Approach to Enhance Circularly Polarized Vortex Wave Antenna

We proposed a metalens-loaded structure to produce a vortex wave of right-hand circular polarization (RHCP) whose orbital angular moment (OAM) is mode -1. The metalens consists of various elemental rectangular cavities arranged in two directions on a two-layered substrate. The rectangular element employs PEC vias as the substrate integrated waveguides (SIW), two substrates printed with two variable-direction double-split square metal patches on the top and bottom, and an air gap between two substrates. According to the Pancharatnam-Berry phase principle, the proposed meta-atoms characterize a phase range of 0°-360° and stable transmittances over 0.8 with the patches rotating 0°-180° around their center. An OAM generator adopts a sequential rotation array of four identical patches of isosceles right triangles with symmetric tangent angles. Compared with the single antenna without the proposed metalens, the loaded antenna achieves a 5.04 dB enhancement in gains and a 32.4° reduction of lobe widths.