Design And Electromagnetic Properties Of Broadband Stealth Metamaterials Based On Multiple Mechanisms

Radar stealth weapons play a vital role in winning the future information warfare,and has been widely concerned by various countries.There are two main methods to achieve the stealth of weapons.One is to reduce the radar cross section(RCS)by shape design,and the other is to apply radar absorbing materials(RAM).Traditional stealth materials are mainly absorbing materials based on microwave absorption mechanism,and their stealth performance in the band of 8-18 GHz has achieved great success.However,due to the intrinsic limitations on electromagnetic parameters and dispersions,traditional absorbing materials have encountered bottlenecks in further improving performance and broadening the working band.Hence,researchers turned interest to stealth metamaterials.However,metamaterial absorber has the drawback of narrow working band due to its resonance absorption mechanism.Recently,low-scattering metasurfaces are attractive because of its unique advantages in manipulating electromagnetic wave propagation and wider operating band.But it cannot avoid the performance limitations brought by its single working mechanism.Based on above analyses,we design the hybrid metasurfaces with the combination of traditional microwave absorbing materials and metasurface and fully utilize the absorption and scattering of electromagnetic wave to achieve ultra-wideband RCS reduction.The specific work is as follows:1)The complementary working bands of various metamaterial cells are adopted to extend the RCS reduction band of low-scattering metasurface.The design principle is revealed by theoretical calculation.Two sets of metamaterial elements are designed,which are square patch,square ring and 45°,135° short cut-wire cells.They are arranged in a chessboard configuration to form metasurface,which realizes the extension of the RCS reduction bandwidth.The above scheme is confirmed by simulation and experiment,which lays a foundation for the following design of the hybrid metasurface.2)The scheme of combining traditional absorbing materials with metamaterials is proposed.The horizontal and vertical cut-wire units are designed.The metamaterials and magnetic absorbing materials(MAM)are adopted as two basic elements to form the hybrid metasurface.The two parts are in a chessboard configuration.A scattering field calculation formula is derived for the hybrid design,in which the MAM and electromagnetic band-gap(EBG)metasurface have complementary dominant working bands.Moreover,they are able to achieve strong RCS reduction in broad band by working together.The as-designed hybrid metasurface show in both simulation and experiment an unprecedented broadband RCS reduction of-6 ~-15 dB in the frequency range of 5-34 GHz at a thin thickness of 2 mm.3)We propose to combine the scattering metasurface with structural absorbing material to improve the stealth performance of the hybrid structure in low frequency regime.Meanwhile,its good performance in high frequency band is maintained.The honeycomb absorbing material is used as the intermediate dielectric layer,and the horizontal and vertical cut-wires are covered above it to form a hybrid metasurface.Combining the absorption and scattering effects,the RCS reduction band is extended to the low frequency and stealth performance is enhanced.In conclusion,the excellent properties of traditional absorbing materials and the designability of metamaterials are fully utilized for the hybrid design.Through the combination of absorption and scattering redirection,we have realized the band extension of RCS reduction,especially to the lower frequency region.This work has a good inspiration for the combination of metamaterials and traditional materials,as well as the integration of multi-mechanism stealth.