Research And Design Of Electromagnetic Wave Regulation With Phase Gradient Metasurface

Metamaterial is a kind of synthetic electromagnetic material,which has properties that many natural materials do not possess.In recent decades,metamaterials have been applied in many fields,such as beam convergence,polarization conversion of electromagnetic wave,electromagnetic stealth,frequency selection,etc.Compared with metamaterial,metasurface have the advantages of small size,low loss and low cost,and have been widely concerned and studied.As an important part of metasurface,phase gradient metasurface is formed on anisotropic metasurface with phase gradient by using sub-wavelength units with different phase shifts arranged in space according to a certain rules.The phase gradient metasurface can freely regulate the propagation of electromagnetic waves by using pre-designed gradient periodic element.In this paper,the control of electromagnetic waves by phase gradient metasurface is studied.The characteristics and optimization methods of reflective and transmissive phase gradient metasurface are studied.Besides,frequency selective surfaces are used to combine the two kinds of phase gradient metasurface together.At last,their applications are designed and simulated.The details are as follows:In the first chapter,we introduce the metamaterial,metasurfaces and phase gradient metasurface,and review the related research on phase gradient metasurface in China and abroad.Finally,the research content is introduced.In the second chapter,the generalized Snell's law is introduced firstly.Then some basic parameters of the antenna are introduced,and the phase gradient metasurface phase compensation method is introduced.Finally,two applications of phase gradient metasurface to electromagnetic wave control are introduced.In third chapter,a cross element reflective phase gradient metasurfacce element is designed.The element performance is analyzed and an array is composed by the elements.The beam convergence performance is achieved.Secondly,the transmission phase gradient metasurface element is studied.To overcome the shortcomings of low transmission coefficient and small phase coverage angle of single-layer element,methods of multi-layer structure and using metal pins to connect the upper and lower layers are used respectively.Wide phase coverage angle and high transmissivity are realized.The two elements are arrayed in arrays,respectively,and beam convergence performance in transmission direction is achieved respectively.In the fourth chapter,the traditional reflective phase gradient metasurface is replaced by frequency selective surface and a dual-frequency and bidirectional phase gradient metasurface element is designed.The horn antenna is used as the feed,and the beam can be converged in the two directions of reflection and transmission through the array.Finally,the dual-frequency bidirectional phase gradient metasurface is fabricated and tested,and the simulation results are basically consistent with the test results.In the fifth chapter,two arrays are designed by using the unit designed in the fourth chapter.The first arrays realize the generation of dual-frequency,bidirectional and dual-mode orbital angular momentum waves,and the second arrays achieve the performance of RCS reduction and beam convergence.