Design of broadband transmission vortex wave array antenna based on metasurface

In this paper, a broadband vortex wave array antenna based on a metasurface is designed. The array antenna unit consists of three metal layers and two dielectric substrate layers, and the top layer and bottom layer are mutually orthogonal metal gratings which form a Fabry-Perot cavity to improve the polarization conversion efficiency. By changing the opening angle and relative position of the intermediate C-shaped ring, 360° phase coverage can be achieved. By adjusting the width of the metal gratings, the transmission amplitude is more than 0.9 from 13 GHz to 20 GHz, resulting in the extended operating bandwidth. The experiment results show that the designed array antenna achieves a polarization conversion rate of 0.99 and generates orbital angular momentum (OAM) vortex beam pointing at (θ,φ,l) = (15°, 0°, +1) in the range of 13-20 GHz with a maximum gain of 19.8 dBi.