Research And Design Of Novel Broadband Stealth Metasurface

With the continuous breakthrough of science and technology,electromagnetic wave(EM)plays an increasingly important role in modern communication systems.However,in the battlefield environment,due to the unprecedented development of detection technology,various new radars have been researched and invented.Therefore,the stealth performance of various aircrafts and ships have also attracted more and more attention.At the same time,the traditional radar stealth technology has completely failed to meet the needs of modern warfare,the development of traditional stealth technology is becoming more and more urgent.Especially to reduce the radar cross section(RCS)in a wide frequency range,therefore the ultra-wideband reduction of the target RCS has extensive theoretical research and application value in the radar detection.In recent years,with the development of artificial electromagnetic metamaterials,electromagnetic metasurface as a two-dimensional artificial composite structure has attracted the attention of more and more researchers,which consists of a certain regular sub-wavelength structures,by adjusting its structure and arrangementcan flexibly control the amplitude,phase,polarization mode,propagation mode and wavefront characteristics of electromagnetic waves.These advantages provide new ideas for designing stealth materials.In this paper,the design method of ultra-wideband RCS reduction based on electromagnetic metasurface is mainly divided the following parts:The first part is based on the design principle of ultra-wideband polarization conversion unit cell,and proposes an wideband and high-efficient polarization conversion unit structure.Then,the principle that the unit structure can realize the polarization conversion of electromagnetic waves in a wide frequency band is analyzed,and the effects of different parameters on the polarization conversion characteristics and the amplitude and phase of electromagnetic waves in the unit structure are also discussed.Finally,the designed polarization conversion unit structure is used to design a wideband RCS reduction metasurface in a chessboard like configuration.Compared with the traditional stealth material,the designed stealth metasurface has a better performance,and the bandwidth of RCS reduction is wider.As a novel artificial electromagnetic material,the polarization conversion material has excellent application prospect in the microwave band due to its excellent amplitude and phase regulation ability.The second part mainly introduces the designed diffusion-like RCS reduction metasurface based on ultra-wideband polarization conversion unit cells.The metasurface consists of polarization conversion units,and the concept of coding is introduced into the design process,by evaluating and optimizing the farfield of the artificial electromagnetic metasurface to obtain an optimal coding arrangement,the broadband RCS reduction is realized,and the farfield scattering is similar to diffuse reflection.Finally its effectiveness is verified by experiments.The third part focuses on the method of further expanding the RCS reduction bandwidth based on multiple sets of polarization conversion units.Based on the asymmetric double-open ring polarization conversion unit,multiple sets of units are designed by changing the structural parameters to realize the discrete 3-bit coding phases(with eight phase states of 0,?/4,?/2,3?/4,?,5?/4,3?/2 and 7?/4).Multiple sets of discrete phase unit arrays are used to further expand the RCS reduction bandwidth and the relative bandwidth is over 90%.The multiple sets of units are randomly arranged so that the scattering energy is approximately evenly distributed,exhibiting diffuse reflection characteristics,and greatly reducing the backward scattering intensity.The designed two types of diffuse-reflective and ultra-wideband RCS reduction metasurfaces based on random code verify the effectiveness of the proposed method.