Research And Design Of Coding Metasurface Applied To Beam Reflection

The coding metasurface introduces the concept of binary digital “0” and “1” in digital circuits and combines the metasurface with digital coding technology,which can conveniently and flexibly control electromagnetic waves.It has important applications in the reduction of radar cross section and the manipulation of beam.In this paper,the reflective coding metasurface is taken as the research object,and the coding scheme of farfield reflected beam design is studied.Based on this,the design and implementation of the metasurface structure is of great academic value and engineering significance.The main research contents are as follows.1.Research on coding scheme for designing the number of reflected beams in the farfield.First,based on the generalized snell reflection law and the combination of gradient sequences of different lengths,a coding scheme of one-dimensional sequence is proposed,which can realize the design of the number of reflected beams in the corresponding plane.Then,based on the theory of the coding metasurface far-field scattering,a 1-bit addition rule is proposed.Two orthogonal one-dimensional sequences are added to obtain a new sequence,and the number of far-field reflected beams is the product of the number of reflected beams of the original two sequences.The simulation results are consistent with the theoretical analysis.2.Research on coding scheme for designing the angle of reflected beams in the farfield.First of all,based on the coding research of 2-bit metasurface single-beam reflection and according to the need of specific reflection angle,two 2-bit single-beam sequences are superimposed by using the 2-bit addition rule to realize the design of single-beam reflection angle.After that,multiple 2-bit single-beam coding sequences are superimposed by using the addition theorem on complex codes to obtain multi-beam reflection of different angles,so the number and angle of reflected beams can be controlled.The simulation results are consistent with the theoretical analysis.3.Design of multi-beam reflection metasurface based on 1-bit coding.First,a small metal rod structure is adopted,and two metasurface units with a reflection phase difference of 180° are obtained by rotating the structure.Then,two one-dimensional sequences with four and three reflected beams are designed,and the coding scheme for designing the number of reflected far-field beams is used.The designed metasurface structure composes of 12×12 grids.The simulation results show that in a wide frequency band(8.8?21.8GHz),the metasurface combines the reflected beams of two sequences,and the number of reflected beam is 12 beams.4.Design and implementation of dual-beam reflection metasurface based on 2-bit coding.First,through the adjustment and optimization of the hexagonal arrow structure parameters,eight metasurface units with a reflection phase interval about 45° are obtained.After that,two sequences with reflection azimuth angles of 90° and 315° are completed as required.Utilizing the coding scheme for manipulating the angle of reflected beam,a metasurface composed of 20×20 grids is designed and machined.The measured results show that the metasurface has two reflection beams at the working frequency of 28 GHz,and the azimuth and elevation angles are 90°,28° and 315°,29°,respectively.The measurement and simulation results are basically the same.