Novel Ultra-Broadband And High-Performance Electromagnetic Metasurface For RCS Reduction

Traditional radar stealth methods generally use radar absorbing materials,active cancellation technology,or change the shape and structure of the target.These technologies have certain limitations due to their high cost,hard to conform to the equipment,and their immaturity.Due to the advantages of light weight and low loss,the electromagnetic metasurface has great research value in the field of electromagnetic stealth in recent years.In this paper,the research status of the coding metasurface and absorption-diffusionintegrated metasurface at home and abroad is analyzed.At the same time,the fundamentals of antenna scattering are introduced.The concept of radar cross section is introduced in detail and the formula derivation is given,then the analytical model of the antenna scattering matrix is given,the composition of antenna scattering is clarified.In addition,this paper analyzes and derives the basic theory of electromagnetic metamaterials,including the classification and derivation process of generalized Snell’s law,the calculation electromagnetic wave absorption rate,and loss mechanism of electromagnetic wave.In this paper,an ultrawideband coding metasurface using period changed unit cell and an absorption-diffusion-integrated metasurface for high-performance radar cross section reduction are designed to improve the operating band and performance of RCS.(1)An ultrawideband diffusion coding metasurface based on period changed unit cell structure is designed.Different with the traditional coding elements,the "0" elements is composed of 2×2 small unit cells with a small period,realizing the ultrawideband reflection phase difference of 180°±37° between the two coding elements,a simulated annealing algorithm was employed to seek an optimal sequence of the metasurface.Simulation results show that the metasurface enables a 10 d B monostatic RCS reduction over an amazing ultrawideband ranging from 7.1 to 29.2 GHz(BW of 122%)while maintaining polarizationinsensitive property.Under oblique incidence,the bistatic RCS reduction can also maintain the broadband characteristics.For verification,the metasurface is fabricated and measured,the simulated and measured results are in good consistent with each other.The design method of this metasurface is verified.(2)An absorption-diffusion-integrated metasurface using hybrid copper-graphene structure is proposed.Firstly,we propose two simple hybrid copper-graphene units with similar absorptivity and a reflected phase difference of 180°±37°,which are utilized to construct a novel absorption-diffusion-integrated metasurface by using simulated annealing algorithm with scattering pattern prediction module.The simulated results show that in the case of normal incidence,compared with the metal plate of the same size,the proposed absorptiondiffusion-integrated metasurface with only a single functional layer exhibits more than 20 d B radar cross section(RCS)reduction from 7.5 to 13.5 GHz.Bistatic RCS reduction under oblique incidence angles remains stable while maintaining a lower profile.Simultaneously measured and simulated under monostatic and bistatic RCS reduction results show good consistency.