Research On Leakage Wave Radiation Based On Metasurface

Metamaterials,composed of sub-wavelength electromagnetic resonant units,exhibit unique electromagnetic properties e.g.,negative refraction,perfect imaging,cloaking,etc.,which are difficult to achieve by natural materials.By designing the resonant unit,arbitrary magnetic permeability and dielectric constant can be realized in a specific frequency band,thereby achieving effective control of electromagnetic waves.Therefore,Metamaterials have attracted much attention in many fields and are widely applied in the development of various functional devices.In this paper,a design method of multi-beam leakage wave radiation based on metasurface is proposed.By designing the scalar surface impedance distribution of metasurface,the radiation direction,polarization mode and beam type of the radiation beam can be independently controlled.The main research contents and contributions are summarized as follows:(1)The basic concept of the leaky-wave antenna and the principle of the periodic structure leaky-wave antenna are introduced.The holographic leaky-wave antenna combines the optical holographic principle with the artificial impedance modulated surface.According to the process of impedance modulation,the interference field of the source and target fields is recorded,and then the source field is used to illuminate the impedance modulated surface.The scattering field is the desired target field,which is simpler than the traditional holographic antenna design method.(2)A design aimed at multi-beam leaky-wave radiation on the basis of scalar impedance modulated surface is proposed,and the radiation characteristics of each radiation beam can be designed independently.The metasurface is fed by a coaxial probe.The source field excited by the metasurface is a radially polarized surface wave.The electric-field component parallel to the metasurface in a plane is present in all radial directions.Therefore,not only the radiation direction of the radiated electromagnetic wave(ie,the target field)can be designed,but also the polarization mode of each beam can be designed.Different from the reflect-array,the leaky-wave antenna based on metasurface proposed in this paper integrates the feed source and the radiation surface on the same plane,and has the advantage of ultra-low profile.(3)Seven leaky-wave radiation antennas with different characteristics are designed based on the method of multi-beam leaky-wave antennas applying for artificial impedance surface.1)Three single-beam,differently polarized,leaky-wave antennas,2)three dual-beam polarized controllable leaky-wave antennas,and 3)a dual-beam leaky-wave radiating antenna with different orbital angular momentum.The electromagnetic simulation results show that the number and polarization characteristics of electromagnetic radiation beams can be designed artificially according to the need by designing different surface impedance distributions.At the same time,the leaky-wave antenna with orbital angular momentum beams is experimentally validated.The test results are in good agreement with the simulation results,which proves the correctness of the design of multi-beam leaky-wave radiation method based on artificial electromagnetic impedance surface.