Research On RCS Reduction Technology Based On Metamaterial

With the increasing development of radar technology,the traditional weapons and equipments are facing huge challenges in the modern war because it is easily detected by the radars,and thus electromagnetic stealth technology becomes increasingly important.It is an significant to reduce the radar cross section(RCS)of the object in order tomake it invisible to the radars.In this thesis,based on the metasurface,the design methods for the structure with the low RCS characteristic are studied,and several new RCS reduction metasurfaces have been presented.The main work in the thesis are as follows:1.RCS reduction metasurface design based on characteristic mode method.According to the characteristicmode method,a 4-by-4 polarization rotation subarray is designed to convert the co-polarized component of the RCS into the cross-polarized one,thus reducing the co-polarized RCS.To simultaneously reduce the co-polarized and cross-polarized components of the RCS of the object,the subarray as a super unit cell is arranged into the array in the rotation way to reduce the total far field according to the polarization cancellation.In order to reduce the electrical size of the metasurface for the miniaturization,some slots are etched on the metasurface to lengthen the current patch.Meanwhile a patch is introduced to achieve the RCS reduction in low frequencies.The simulation and measurement results are given to verify the proposed design.In the frequency band of6?20.7 GHz,about 10 d B RCS reduction is achieved.The overall size of the proposed structure is 1.28?×1.28?.Therefore,the ultra-wideband RCS reduction is achieved by the proposed metasurface with the compact size.The characteristic mode analysis used in the proposed design process provides us an effective way to design the metasurface.2.Dual-band RCS reduction metasurface design based on frequency selective surface(FSS)and polarization rotation metasurface.Based on FSS and polarized rotating metasurfaces,a new dual-band metasurface composed of the FSS and polarization rotation metasurface is designed for RCS reduction.By replacing the metal ground of the high-frequency polarization rotation metasurface by a low-pass FSS,the low-frequency plane wave can well propagate through the upper high-frequency polarization rotation metasurface to illuminate the lower low-frequency polarization rotation metasurface,thus achieving the dual-band polarization rotation metasurface.Furthermore,the dual-band polarization rotation metasurface is translated and rotated to achieve a new array for far-field cancellation in the two frequency bands.With the simulation and the measurement,the dual-band metasurface can achieve over 10 d B RCS reduction in the band of 6.6-12.7GHz and 27.9-38 GHz bands,respectively.3.Automatic design of polarization rotation metasurface.Based on the optimization algorithm NSGA-II,an automatic design of the metasurface with the polarization rotation characteristic has been developed by Matlab programming control.A metallic patch is divided into some small square meshes.With the NSGA-II,these meshes are coded,and meanwhile the polarization rotation characteristic generated by these meshes are chosen as the fitness function.The metasurface structure composed of these meshes is automatically determined by optimizing the fitness function.The optimized metsurface structure is arranged into an array in the rotation way for the RCS reduction.With the proposed optimization method,two metasurface structures are designed in the single and dual frequency bands,respectively.With the two metasurfaces,the corresponding RCS reduction structures have been developed.Simulation results are given to demonstrate the effectiveness of the proposed optimization method.