Study On Artificial Dielectric Electromagnetic Metasurface In Stealth And Polarization Conversion

Metasurface is a two-dimensional metamaterial,composed by an array of the sub-wavelength electromagnetic resonators.A series of new electromagnetic functions can be realized with the metasurface,which becomes a hot field for scientific research and engineering application.Metasurface can be divided into metal-based metasurface and dielectric-based metasurface.The metal-based metasurface achieves the ideal electromagnetic amplitude and phase distribution mainly by adjusting the shape and size of the metallic unit.However,the metal elements is limited in some special applications such as high corrosion and high temperature environment.While the dielectric-based metasurface has excellent advantages in the above applications due to its excellent physical and chemical properties.Therefore,this paper focuses on the theory of dielectric-based metasurface and its potential application.The main contents of this paper are as follows:(1)The concept,as well as the state of art of stealth technology are studied,and a design method of low scattering dielectric metasurface is proposed.The principle of dielectric resonator and the low scattering metasurface are discussed in detail.A dielectric-based unit cell is designed in contrast to the normal metal-base unit structure constituted by a square cube and a metal ground.Then a low scattering dielectric metasurface device is designed.Simulation and experimental results show that the device has excellent stealth properties in Ku-band stealth requirements.(2)A reflective polarization converter based on dielectric metasurface is designed based on Fabry-Perot principle.The unit cellof polarization converter consists of a dielectric cube and a metal plane,where long axis of the cube is parallel to the vertical direction.The simulation result shows that the cross-polarization conversion rate is over 90%in 8.7GHz-12.5GHz.The polarization converter has the advantages of broad bandwidth,simple structure and high polarization conversion efficiency.(3)A dielectric metasurface with orbital angular momentum(OAM)is designed according to the spiral phase method.The basic unit takes the same form as that used in the third chapter.It can realize full phase by changing the length and width of the dielectric cube.Simulation results show that the bandwidth of the proposed OAM device can be obtainted as large as 5 GHz.A deflected OAM device is designed and the beam of the device can be deflected into the desired direction.