The Design Of Metasurface Vortex Electromagnetic Wave Convergence Lens

In recent years,with the rapid development of wireless communication technology,people's living standards have been greatly improved.The increasing number of wireless terminals and the higher speed requirements for wireless communications still require new technologies to increase communication rates and spectrum utilization.In this case,the new technology of orbital angular momentum has entered people's field of vision.The vortex electromagnetic wave is an electromagnetic wave carrying Orbital Angular Momentum(OAM),which utilizes the orthogonality between different OAM modes,and uses vortex electromagnetic waves with different OAM values as carriers to multiplex transmission.The carrier wave modulates the multi signals onto the electromagnetic waves of different OAM modes at the same frequency point,which becomes a potential method for effectively improving channel capacity and spectrum efficiency.However,the vortex electromagnetic wave has a hollow characteristic,and its divergence increases with the increase of the distance and the OAM mode,which limits its application in long-distance communication.Aiming at the divergence of vortex electromagnetic waves,this paper proposes a design and implementation method of metasurface vortex electromagnetic wave convergence lens based on phase modulation.The main research contents are as follows:Firstly,the basic concepts and characteristics of vortex electromagnetic wave and metasurface are studied.The exploration of the inherent properties and production methods of vortex electromagnetic wave,the modulation principle of metasurface electromagnetic wave using metasurface,the theory of phase mutation and the basic classification of metasurface,these provides a theoretical basis for the design of metasurface vortex electromagnetic wave converging lens.Secondly,by studying the characteristics of Laguerre Gaussian beam and Bessel beam,and referring to the design principle of axicon lens which produces non-diffractive high-order Bessel beam,the phase modulation method is proposed and the phase compensation theory of metasurface convergence lens has been deduced.Then the transmission metasurface unit structure is designed,the simulation and analysis of its transmission phase and transmission amplitude are carried out,and the appropriate metasurface unit structure is selected to lay the foundation for the realization of the metasurface vortex electromagnetic wave converging lens.Then,the MATLAB-HFSS-API script file is used to quickly build a metasurface vortex electromagnetic convergence lens model,and the simulation software ANSYS HFSS is used for preliminary simulation.The near-field electric field amplitude distribution,farfield two-dimensional and three-dimensional gain distribution,phase distribution before and after convergence,transmission efficiency and OAM purity were analyzed to verify the good performance of the metasurface convergence lens.Finally,through the PCB technology,the designed lens is made into a physical sample for microwave darkroom experiment.The experimental results of near-field normalized electric field amplitude distribution,far-field two-dimensional gain curve and phase distribution before and after convergence are simulated.In contrast,the engineering achievement performance of the lens was verified,and the work of the entire subject was completed.