Antennas Design For A Novel Near-Field Communication System

In this paper,a novel Fresnel radiative region near field wireless communication system based on orbital angular momentum phase mode is studied,especially antenna design for this system.According to our former research,the orthogonal phase mode of multi-order orbital angular momentum can be used for channel multiplexing.Taking the circular array antenna as an example to show the channel matrix and multiplexing process.We proposed and designed a novel phase shifter for array antenna system.We proposed a reflector antenna array with parabolic loop reflecting surface for generating the orbital angular momentum modes in this paper.Comparing to the array without reflecting surface and the array with conventional parabolic reflecting surface,this reflector array shows good performance in focusing the electromagnetic waves,and thus obtains higher gains at the first beams of all the transmitted orbital angular momentum modes.We design different sub-wavelength structures using emerging electromagnetic material.The two-dimensional periodic array can control the phase of the reflected wave more than 360°,ensure the amplitude and polarization of the reflected wave without change,and apply this structure to a linearly polarized reflective array antenna.The phase expression for generating different orders of orbital angular momentum is given.The antenna array is designed and analyzed by the full-wave electromagnetic simulation software.Aiming at shortcomings of the above mentioned reflective array antenna,we propose a surface mode to OAM mode transformation antenna by using metasurface in this paper.The principle and expression of the design are deduced,and the expression of the phase for generating different order orbital angular momentum beam is given.Multiple different order orbital angular momentum beams can be generated.The parameters of the antenna are given through theoretical derivation,numerical simulation and experimental test.The simulation and experimental results show good consistency,which meet the design expectation.