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

Abstract

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 capacity of wireless communication systems.

Recent progress on RF orbital angular momentum antennas

“…The multiple and tunable features in real-time are the inevitable trend in RF OAM metasurface antenna designs [104]. It is easy for a single metasurface to generate multiple OAM modes by using the superposition of the aperture field or other methods [105][106][107][108][109]. As depicted in Figure 13(a), dual-modes with different radiation directions were obtained by a single metasurface [110].…”

Ultrathin dual-mode vortex beam generator based on anisotropic coding metasurface

“…Compared to traditional spiral reflectors and antenna arrays, metasurfaces not only show advantages of low profile, small mass, low manufacturing cost, and ease of deployment, but also establish the feasibility of mode multiplexing of OAM beams. In general, there are several basic techniques for OAM mode multiplexing, including multiband 34 , direction 35 and polarization 36 – 38 . In 2018, Meng et al proposed dual-band reflectarray for generating dual beams with respect to carrying two different OAM topological charges operating in different bands 34 .…”

“…In 2018, Meng et al proposed dual-band reflectarray for generating dual beams with respect to carrying two different OAM topological charges operating in different bands 34 . Also in 2018, Meng et al proposed an anisotropic holographic metasurface to generate multiple beams with different orbital angular momentum (OAM) modes in different directions 35 . Polarization multiplexing relies on the use of polarization state as an additional degree of freedom.…”

Generating Different Polarized Multiple Vortex Beams at Different Frequencies from Laminated Meta-Surface Lenses

“…Meta-surfaces have been proved to be an efficient way to generate OAM vortex beams through properly arranging sub-wavelength meta-atom arrays [8][9][10][11][12][13][14][15][16], where multiple OAM vortex beams with controllable beam directions and topological charges have been synthesized [17][18][19][20][21][22]. On the other hand, meta-surfaces have also demonstrated the great capacity of polarization conversions [23][24][25][26][27][28], where linearly polarized (LP) waves are shown to be transformed into their cross counterparts through re-assigning the amplitudes of co-and cross-polarized components.…”