Low Scattering Electromagnetic Metamaterial Design And Its Application In Antenna RCS Reduction

At present,all countries in the world spend a lot of money and manpower on the research of stealth weapon platform.In the design of stealth weapon platforms,controlling the overall Radar Cross Section(RCS)of the weapon platform is beneficial to reduce the detection distance of enemy electronic detection system and reduce the deterrence range of enemy weapon system,so as to improve the penetration and survivability of our weapon platform.Antenna is the main scattering source of stealth weapon platform,how to ensure the normal radiation work of antenna,effectively reduce its RCS is the focus of stealth field.Electromagnetic metamaterials have the advantages of small size,low loss and easy integration,and can effectively regulate electromagnetic waves,which provides a new idea for the RCS design method to reduce the target,and shows a broad application prospect in the field of stealth.This thesis focuses on the design of low scattering metamaterial and its application in antenna RCS reduction.The main contents are as follows:1.A kind of ultra-wideband low scattering metamaterial based on a mixing mechanism is designed and applied to RCS reduction of the circularly polarized array antenna.The designed metamaterial is a kind of metamaterial that combines polarization conversion metasurface and water absorber,and uses diffusion and absorbing mechanism to realize the low scattering characteristics of ultra-wideband metamaterial.Since the influence between water and polarized conversion metasurface is very small,the two RCS reduction bands can be continuously combined to achieve ultra-wideband RCS reduction.The metamaterial basic unit is designed first,and its co-polarization reflection coefficient is less than-10 d B in the2.8-80GHz(relative bandwidth of 186.4%)frequency band.Then,a 12×12 chessboard metamaterial was formed.The metamaterial achieved RCS reduction of more than 10 d B in the 2.8-80 GHz frequency band,and the simulation results were basically consistent with the measured results.Finally,a 6×6 metamaterial was integrated with a dipole antenna to design a circularly polarized antenna element.Then,the circularly polarized antenna element was arranged into a 2×2 circularly polarized array antenna and the feed mode adopts sequential rotation feed.The results show that the circularly polarized array antenna has good radiation performance.Its-10 d B reflection coefficient bandwidth is 2.6-3.3GHz,its 3d B axial ratio band is 2.78-3.25 GHz,and its maximum gain is 11.3d Bi at 2.95 GHz.At the same time,the array antenna has the characteristics of low RCS in the operating band of 2.6-3.3GHz,the maximum RCS reduction is up to 26 d B,and also achieves a certain degree of RCS reduction in the out-of-band.2.An active stealth coding metasurface based on polarization control is designed.Firstly,a1-bit coding reconfigurable polarization conversion metasurface element was designed.In the 8-12 GHz frequency band,the co-polarized reflected wave amplitude of the element was less than-10 d B in the coding states(0,1)and(1,0),which realized the rotation of incident wave polarization.At the same time,the reflection phase difference of the element in the two states is ±180°.Then,the RCS reduction performance of the 10×8 scale metasurface is simulated,and the RCS reduction can reach 10 d B in most frequency bands of 8-12 GHz,and the maximum RCS reduction value can reach 16 d B.Finally,to verify the correctness of the simulation results of the active stealth coding metasurface,a 20×20 scale active stealth coding metasurface was manufactured.In the control circuit part,The FPGA control circuit board was used to control the state of the PIN diodes.The test results showed that the metasurface under the stealth regulated state achieved RCS reduction of more than 10 d B at8-12 GHz.The maximum RCS reduction is 31 d B.3.A low scattering dual-band polarized conversion metasurface is designed.Firstly,a 1-bit coding polarized conversion metasurface element is designed.The frequency bands of the coding element "0" with the co-polarization reflection coefficient less than-10 d B are 10.1-13.7GHz and 14.7-22.5GHz,and its mirror element is the coding element "1".The reflection phase difference between the two is ±180° in the 6-24 GHz frequency band.Then,the RCS reduction characteristics of the metasurface(array size 6×6)with different cycles of the01/10 coding scheme are analyzed.The simulation results show that the RCS reduction capability and bandwidth of the metasurface increase with the increase of the cycles of the compact cells.Finally,when the number of cycles of compact cells is 4,the RCS reduction characteristics of the metasurface with different coding sequences are simulated.The results show that the metasurface with 01/01,01/10 coding pattern and the whole checkerboard pattern can achieve more than 10 d B RCS reduction in the frequency band of 10.1-13.7GHz and 14.7-22.5GHz.At the same time,it exhibits specular reflection characteristics around13.5GHz.Finally,the 01/01 sequence coding metasurface was processed and tested,and the monostation RCS measurement of metasurface was basically consistent with the simulation results.