| Terahertz(THz)wave is electromagnetic wave between microwaves and infrared waves,and has a higher imaging resolution than microwaves and a stronger penetrating power than infrared visible light,which endows it with the advantages of both microwave communication and optical wave communication to a certain extent.Terahertz radar technology has broad development prospects in military,medical,security and other fields.Stealth technology,as an effective means to improve the survivability of combat weapons and break through the enemy's defense capabilities,is of great significance to the development of national defense military,and an important indicator of the quality of target stealth performance is the Radar Cross Section(RCS).The RCS characteristics of target stealth and its imaging are the technical basis of terahertz radar military application.However,due to the short wavelength of the terahertz,the phase sensitivity,and the detection technology is not yet mature,the calculation,measurement,and reduction of the target RCS in the terahertz band still face many urgent issues to be studied.Now,the major methods to reduce RCS contain shape design,loading radar absorbing materials,etc.,but these methods have a large impact on target radiation performance.Under this application background,this paper conducts research on the encoding matasurface in the terahertz band,and uses the phase modulation characteristics of the electromagnetic metasurface to regulate the direction of electromagnetic wave propagation,providing a new way to achieve the reduction of broadband RCS.The main research innovations can be summarized as follows:1.Based on the theory of metamaterials and electromagnetic metasurfaces,the high-frequency three-dimensional electromagnetic field simulation software CST Microwave Studio based on the time-domain finite integral method is used to perform structural modeling and simulation analysis of 1bit and 2bit electromagnetic metasurfaces structure,and data processing is performed using Matlab.2.A 1-bit coded metasurface structure is composed of two basic digital elements and adjacent elements.The 180° phase difference between them reduces the radar cross section(RCS)by non-directional scattering at a wideband THz frequency.Compared with the existing research results,the reduction of the RCS of the electromagnetic metasurface structure we designed is larger,up to 15-26 d B,which has the characteristics of no direction,broadband and low scattering.3.On the basis of the 1-bit coded metasurface structure,a wide-band,large-angle,polarization-insensitive,and low-scattering 2-bit coded metasurface structure is designed.The aspect reflects the excellent characteristics of the structure.The surface layer is based on a symmetrical double cross metal strip structure and four digital coding units "00","01","10",and "11" with a phase difference of 90°,which can transmit terahertz waves incident vertically.Multiple beams are generated and a diffuse reflection effect occurs.For a 1-bit coded metasurface structure and a flat metal plate structure of the same size,this coded metasurface can achieve the characteristics of wider frequency band,low scattering,large angle,and polarization insensitivity,thereby reducing the effect of radar cross section. |
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