Generating Multiple Orbital Angular Momentum Vortex Beams From Meta-surfaces Antenna

The demands for communication capacity of communication technology are increasing sharply nowadays.Due to the good orthogonal between different modes,the orbital angular momentum(OAM)vortex waves can form rich same-frequency multiplexing channels and show great potential in expanding communication capacity.The generation of OAM vortex waves is critical,thus the design of antenna is particularly important,and the metasurface are widely used in the design of the vortex beam antenna due to its powerful ability to regulate the electromagnetic wave and easy to implement.In addition,the multiple-beams methods are also introduced into the design of vortex beam antenna to further expend the communication capacity and coverage.The main contents and work are as followed:1.We explained the differences between metamaterials and metamaterials in analysis methods and deduced the general Snell law.Then we imployed the typical metasurface mode to demonstrate the principle of metasurface regulating electromagnetic waves.The basic theory and several generation methods of the OAM vortex waves were introduced,and we also demonstrated the generation of the OAM vortex waves.2.We proposed a two-dimensions vortex beams scanning antenna based on Rotman lens which realizes the two-dimension vortex beam scanning.Firstly,an active transmission metasurface with electrically controlled phase was proposed,which can generate vortex beams and scan along the x direction when illuminated by vertically incident waves.Then we designed a Rotman lens to generate beams scanning along the y direction.Finally,we used the Rotman lens antenna illuminated the active meta-surface,which effects were equivalent to the meta-surface radiated by the oblique incident wave alongy direction.The vortex beams could scan along the x direction by changing the bias voltages of the metasurface elements,and changing the input ports of Rotman lens antenna could make vortex beams scan along y direction,thus the two-dimensions scanning of the vortex beams are realized.3.We demonstrated the generation of multiple orbital angular momentum(OAM)vortex beams through a dual reflecting Cassegrain system formed of a secondary meta-mirror with polarization conversion functionalities and an anisotropic primary meta-mirror capable of prescribing multiple OAM vortex beams of different characteristics.More specifically,electromagnetic fields from the feed would be firstly reflected by the secondary meta-mirror with linear-to-circular polarization conversions,and then transformed into well converged multiple OAM vortex beams by the primary meta-mirror,where the radiation directions,polarizations and topological charges of every single OAM vortex beams could be specifically prescribed.Especially,we are able to create different polarization states of the multiple OAM vortex beams when the secondary meta-mirror is rotated or equipped with active circuits to illuminate different circularly polarized incidences.Our design,using Cassegrain meta-mirror system to synthesize reconfigurable multiple OAM vortex beams,should pave the way for building up more advanced multiplexing vortex beam communication system with expanded channel capacity.