Technology Of Broadband RCS Reduction Based On Metasurfaces

As an effective means to improve the ability of survival and penetration of combat weapons,stealth technology is of great significance to the development of national defense and military affairs while radar cross section(RCS)is an important indicator of the target stealth performance.Antenna,as a major contributor to the low-visibility platform,taking into account it's radiation performance and scattering performance is a key technical issue for the radar target.Under the background of this application,researches focus on polarization conversion metasurfaces and 1-bit coding metasurfaces are carried out.The polarization and propagation of the electromagnetic waves are controlled by the phase modulation of the metasurfaces,which provides a new way to the realization of broadband RCS reduction.The main contents and achievements of this thesis are as follows:First,based on the RCS reduction mechanism of artificial magnetic conductor(AMC)structures and the polarization characteristics of electromagnetic waves,a novel polarization conversion metasurfaces is proposed and applied to broadband RCS reduction.The metasurfaces is created by the combination of an oblique split ring resonator(SRR)and a cur-wire resonator,which is capable of converting a linear polarization state into its orthogonal one.The simulation results show that the 10 d B bandwidth of polarization conversion is obtained in wideband from 9.4 to 19.2GHz,with an average polarization conversion ratio(PCR)of nearly 100%.Due to the high PCR,monostatic RCS reduction of 10 d B can be realized over 60% frequency bandwidth with respect to the equal-sized PEC ground plane under normal incidence.Second,a low RCS microstrip antenna is designed by loading metamaterials.By loading polarization conversion metasurfaces around radiation patch,the backscatter of the antenna can be reduced without changing the size of the original antenna.The simulation results show that the radiation performance of the antenna is not affected after the loading of the metasurfaces.Under normally x-polarized and y-polarized incident waves,the proposed antenna has obtained significantly RCS reduction from 7 to 24 GHz with respect to the reference antenna.The 5d B bandwidth of monostatic RCS reduction is achieved in wideband from 8.9 to 19.4GHz.It can be seen that the polarization conversion metasurfaces provides a new design idea for antenna RCS reduction.Third,a novel 1-bit coding metasurfaces which can achieve broadband RCS reduction within microwave frequency band is proposed.The metasurfaces is composed of “0” and “1” elements.The reflection phase difference of the two elements is about 180? in broad frequency band.By designing the coding sequences of the coding metasurfaces,broadband RCS reduction is obtained as a result of the diffuse reflection.Full-wave simulation results show that the monostatic RCS reduction more than 10 d B for coding metasurfaces can be achieved in a wide frequency range from 10-20.75 GHz with respect to the equal-sized PEC ground plane under normal incidence.Compared to the equal-sized chessboard with same unit cells,the relative bandwidth of 10 d B RCS reduction is increased by 25%.As an effective means to reduce RCS,the coding metasurfaces shows great potential applications in stealth technologies and antenna designs.