Research On Electromagnetic Stealth Based On Phase Gradient Metasurface

With the development of radar detection technology,it is of great significance to study flexible regulation of Radar Cross Section(RCS)for improving the survivability of passive equipments.The thesis mainly studies two types of phase gradient metasurface(PGM),which are respectively based on the principles of spoof surface plasmon polaritons(SSPP)and anomalous reflection.Both of them have a significant effect on the reduction of monostatic RCS,and the latter one also has the function of camouflage.The main contents and contributions are shown as follows:(1)Based on SSPP,phase gradient metasurfaces of bilaterally bent square-ring are designed.By changing reflected waves into surface waves,RCS can be effectively reduced.The simulation results show that RCS reduction value under vertical polarization(Transverse Electric,TE)reaches a maximum of 7d B;RCS reduction value under horizontal polarization(Transverse Magnetic,TM)reaches a maximum of 10.4d B,and the effective reduce bandwidth reaches to 300 MHz.The measured results are in good agreement with the simulation results,which verifies the effectiveness of the design method based on SSPP.(2)Based on the principle of anomalous reflection,two types of phase gradient metarsurfaces of single loop are designed.First,the reflection angle of the future wave is deflected by 90°,and the effective reduction of RCS in the frequency band of 9.5-10.2GHz is achieved.The average RCS reduction value in this band is 15 d B,and the maximum RCS reduction value is 22 d B.The radar detection distance is reduced to 28%.The measured results agree well with the simulation results.Secondly,by reflecting the incident wave at an oblique 30° according to the original path,the backscattering enhancement is realized,and the best camouflage efficiency reaches 88.8%.(3)Further research on metasurface elements is carried out based on the principle of nesting.By expanding the single loop into double loops,the phase shift curve of element obtains better linearity,thereby achieving more uniform phase compensation.Based on the principle of anomalous reflection,two types of phase gradient metasurfaces of double loops are also designed.First,the reflection angle of the incident wave is deflected by 90°,and the effective reduction of RCS in the frequency band of9.35-10.15 GHz is achieved.The average RCS reduction value in this band is 18 d B,and the maximum reduction value is 31 d B.The radar detection distance is reduced to 16.8%.Compared with the single loop,the effective bandwidth is widened by 100 MHz,and the maximum reduction value is increased by 9d B.Secondly,the backscatter enhancement is realized by reflecting the oblique 30° incident wave according to the original path,and RCS can be improved by 2d B on average in the range of 9.5-10.4GHz.The best camouflage efficiency reached 92.7%,which was 4 percentage points higher than the single loop.