Research On Multifunctional Focusing Electromagnetic Metasurface

With the rapid development of wireless communication,the near-field characteristics of antennas have received widespread attention.In some applications,it is necessary to focus the energy on the near-field region of the antenna,which requires the use of a focused antenna.Focusing antenna with energy concentration in the focus can not only be used to achieve energy transmission and improve the ability of industrial detection,but also be applied to RFID system and near-field sensing imaging,etc.it also has a potential application prospect in the next generation lithography technology.Traditional focusing systems mostly focus on lenses or parabolic reflectors,which are large in size and difficult to process.Metasurfaces have become a new way of focusing electromagnetic waves due to their advantages such as flexible adjustment of electromagnetic waves.The transmissive focusing metasurface uses four or more metal structures to control electromagnetic waves.At present,there are many research results on the far-field focusing beam,but few research results on the near-field focusing.At the same time,there are fewer studies on the multi-functional focusing metasurface with far-field focusing.This paper studies a multi-functional focusing metasurface with fewer metal layers and multi-focus characteristics,and three kinds of metasurface antennas are designed.The main research work and innovations of this paper are as follows:(1)A dual polarized transmission focused metasurface antenna is designed.Firstly,a dual polarization unit with three-layer metal structure is designed as the phase control unit to achieve a larger phase shift range.At the same time,the two polarizations of the unit do not interfere with each other.Secondly,the super surface is designed and simulated,and different phase compensation is carried out for different units to achieve different focusing positions.Different focus positions are set for different polarizations of the metasurface,the results show that the focus position can be changed only by changing the polarization direction of incident wave without redesign.According to the comparison and analysis,the proposed metasurface has the advantages of dual polarization,high efficiency,few metal layers,and multi-function.(2)A dual-frequency and dual-polarization multi-functional reflective and transmissive metasurface antenna is designed.First,a dual-frequency unit is designed,which can achieve360° reflection phase shift under 16 GHz and y-polarized incident waves,and 330°transmission phase shift under 13 GHz and x-polarized incident waves.The unit can be adjusted independently under different polarization and frequency.Secondly,two kinds of metasurfaces are designed.Simulation results show that single beam antenna with 22.8d B gain or four beam antenna with 16.4d B gain can be obtained under reflection,and high efficiency focusing can be achieved under transmission.Finally,one of them was processed and tested.The results showed that the metasurface uses a small number of metal layers to realize the control of the reflection and transmission mode,and has the ability to work in dual polarization and dual frequency bands.(3)A dual-polarized transmission focusing metasurface antenna based on a single dielectric layer is designed.Firstly,a new single-layer cell structure is designed,which achieves 360° transmission phase shift and high transmission amplitude,and achieves dual polarization characteristics.Secondly,single polarization to achieve single focus and single polarization to achieve multi focus are designed.The simulation results show that the designed single-layer metasurface achieves multi-focus characteristics under a polarized incident wave.At the same time,it also has the advantages of dual polarization and multi-function.