Broadband Wave Transparent Material By Frequency Selective Surface With Miniaturized Elements

FSS(Frequency Selective Surface,FSS)as a spatial filter is widely used,such as a radome which can reduce the radar cross section of the antenna.Recently,the research of FSS with miniaturized elements(MEFSS)has attracted a lot attention.Contrast to the conventional FSS,the unit-cell dimension of MEFSS is much smaller than the working wavelength of the electromagnetic(EM)waves.Therefore,the MEFSS can significantly reduce its influence on the transmission or reflection for the EM waves incident obliquely.In addition,with the development of THz technology,THz applications have been attracted more attention by researchers.The main research work includes the following aspects:1,First of all,designed a broadband frequency selective surfaces(MEFSS)working on X-band and Ku-band.From the theory and experimental results,it shows:the structure shows a good performance,-1dB at normal incidence relative bandwidth is up to 64%,and in different directions of polarization and incident at a large angle(60°)still has good transmission performance,theoretical and experimental results coincide.Secondly,in order to further expand the bandwidth,a S-type broadband MEFSS is designed.The-1dB normal incidence relative bandwidth of S-type MEFSS is up to 100%,even at large angles of incidence,it has better transmission performance,and its steep cutoff of the rectangle" of characteristics shows better.On the other hand,these two designed MEFSSs not only has the characteristics of a wide band,and also insensitive to the incident angle and polarization.2,Mainly from the goal of "rectangle" characteristic,a new layered MEFSS is designed,which is constituted by cascaded two MEFSS separated by a spacer.Each MEFSS has two metal layers supposed to be fabricated on a thin substrate.One layer consists of an array of metal strip and other is an array of patch.The simulation and experiment results shows that the layered MEFSS structure not only has good incident angle stability and polarization stability,also it has a good "rectangle" of the filter characteristics.3,Tunable frequency selective surfaces working in THz is designed.First,from the graphene conductivity,dielectric constant,analyzing graphene several common modeling methods,and the use of direct modeling method.It focuses on setting graphene material model in CST.Secondly,analyzes the THz region of several commonly used Cascade frequency selective surface design,analysis of the characteristics of different cascade-type structure,and design based on graphite ene-loaded tunable frequency selective surfaces.Finally,giving the transmission characteristic curve of this structure,on this basis,combined with current and the electric field distribution images,a simplified equivalent circuit model is given for explaining the characteristics of tunable,and analyze the influence of some parameters on the transmission characteristics.