Design Of Phase Gradient Metasurface And Study Of RCS Reduction

As a part of the metamaterial,the phase gradient metasurface is different from other conventional metamaterials.It does not rely on the resonance to absorb the electromagnetic wave for hiding,but instead controls the wavefront of the reflected wave by introducing a phase-shifted wavelength phase mutation on the surface,which cause abnormal reflection and refraction,surface wave coupling,and surface plasmon excitation to achieve stealthy purposes.Based on the previous research,this paper proposes a design concept of "thin and wide" phase gradient metasurface to conquer the disadvantages of large size and narrow frequency band of traditional metamaterials depending on the unique super-surface phase modulation control method.Simulations,experiments,and other methods are used for the studies of phase gradient metasurface performance and explore its characteristics of RCS(Radar Cross Section)Reduction.The main work is as follows:(1)Starting from the Fermat principle of basic principles of optics and the basic boundary conditions of electromagnetics.the generalized Snell's law on the interface is deduced,and the interaction mechanism between the phase gradient metasurface and electromagnetic waves and the singular effects produced are discussed.The two-dimensional generalized Snell's law is generalized to three-dimensional,and the subsequent simulations confirm that the two-dimensional phase gradient metasurface has more scattering ability for electromagnetic waves due to one more phase dimension.(2)Based on the generalized Snell's law;a dual-band phase gradient metasurface with a phase gradient difference of d?(x)=2?/3 is designed.The phase gradient surface combined with two open ring structures meets the phase gradient of d?(x)=2?/3 at the design frequency point and has low reflectivity characteristics.At the same time,the average RCS reduction amounts to 10.3 dB and 10.4dB at the reflectivity valleys of 7.8 GHz and 9.4 GHz.This material thickness is only 0.578mm,about 1/60 of the operating wavelength.(3)Based on the design idea of dual-band phase gradient metasurface,we clarify the design idea of broadband phase gradient metasurface and design a spiral structure with relatively stable phase difference in the range of 12-16GHz.The reflectance characteristic curve shows that it has low reflection characteristics in the design frequency range.Subsequently,the phase gradient is divided into one-dimensional and two-dimensional.The effects of different arrangement methods on the reduction characteristics of RCS are discussed,and the scattering characteristics of the four models are analyzed.Both of them can effectively scatter electromagnetic waves and reduce reflected waves in the direction of the main lobe,thereby reducing the RCS of the super surface.In band of 10-16GHz,the RCS reduction can reach more than lOdB,which further validates our design philosophy.