Generation of multiple beams carrying different orbital angular momentum modes based on anisotropic holographic metasurfaces in the radio-frequency domain

In this paper, an anisotropic holographic metasurface design is proposed, fabricated, and measured, to demonstrate that it can generate multiple beams with different orbital angular momentum (OAM) modes in the radio-frequency domain. The anisotropic holographic metasurface is composed of an array of quasi-periodic square particles with a rectangular slot in the upper metallic layer covered with a dielectric ground. The classic leaky-wave theory and a microwave holography method are introduced to construct the holograms that interfere with the surface waves excited by a monopole antenna and the objective waves represented by the desired multiple beams carrying different OAM modes. Moreover, the numerical simulations and experimental results are in very good agreement, which demonstrates the excellent performance of the design and provides a method of generating multiple OAM modes simultaneously. This lays a solid foundation for a channel-multiplexing method based on OAM-mode multiplexing to expand the capa...