Research On Luneburg Lens Antenna Based On Metamaterial

Luneberg lens is an electromagnetic lens with a gradient of refractive index.It is based on the theory of optical transformation,which converges the incident electromagnetic wave at the focal point,or vice versa.Luneberg lenses have many advantages such as high gain,multi-beam,plane wave generation,etc.It can be used in mobile co mmunications,satellite positioning,electronic countermeasures and other fields.Since the natural materials don’t meet the requirements of refractive index gradient,it is necessary to realize the refractive index gradient distribution of Luneberg lenses by layering,punching or other methods.In this dissertation,the design method and processing method of Luneberg lens are studied.And based on metamaterials,according to the theory of optical transformation,two cylindrical Luneberg lenses are designed.This dissertation mainly includes the following parts:1.The research progress and research status of Luneberg lenses and metamaterials are expounded.The theoretical knowledge used in this dissertation is introduced,including the parameter equivalence method based on strong perturbation theory,the effective parameter inversion theory of metamaterials,the principle of geometric optics,and the basic theory of Luneberg lens.The working principle of Luneberg lens is explained,and the mathematical model of Luneberg lens is deduced.2.Based on metamaterial theory and effective parameter inversion theory,a periodic metasurface design method for Luneberg lens is proposed.The front and back of its unit are crossed metal patches,which can be equivalent to artificial dielectric materials.Its operating frequency is 20 GHz.Through simulation,many factors affecting the equivalent dielectric constant of the material are explored,and the method of changing the equivalent dielectric constant of the material is obtained.Finally,for the designed material processing,the dielectric constant of the material is tested by the waveguide transmission/reflection method,which verifies the feasibility of the design.3.Based on the optical transformation theory and the artificial dielectric materials designed before,a cylindrical Luneberg lens with an operating frequency of 20 GHz is designed.Through theoretical analysis,the waveguide port antenna is selected as the feed source of the Luneberg lens,and the structure of the lens,such as the layering method and size,is optimized by the CST simulation software.Finally,the object is processed,and the antenna far-field radiation pattern is tested in a microwave anechoic chamber environment.The performance of the designed cylindrical By comparing the changes of antenna gain and farfield pattern before and after the cylindrical Luneberg lens,Luneberg lens is verified.4.Based on the parameter equivalence method of the strong perturbation theory,a cylindrical Luneberg lens is designed by using a nylon column with a diameter of 6 mm.It works at5 GHz,and the entire structure is 250 mm in diameter and 150 mm in height.By using the CST simulation software,the influence of the unit structure on the equivalent dielectric constant of the material is first considered.Then the specific dimensions of the nylon column structure of each layer are determined according to the dielectric constant of each layer of the cylindrical Luneberg lens.In order to verify the correctness of the simulation results,the cylindrical Luneberg lens was fabricated and tested in a darkroom,which proved the feasibility of the design.