Research On The Design And Optimization Of An Angle Stable Frequency Selection Surface

Frequency Selective Surface(FSS)is a periodic structure printed on one or more layers of dielectric substrates.Because of its selectivity to electromagnetic waves of different frequencies in space,it is also called a spatial filter.The angular stability of FSS is an important indicator for evaluating its performance.Especially in the military industry,FSS is often used to make radomes to achieve low-loss transmission in the working frequency band,and to achieve electromagnetic waves outside the working frequency band,so as to achieve the purpose of low radar cross section.The FSS with stable angle can ensure that this purpose can be achieved,and then better improve the stealth function of the weapon.In addition,in the current communication field,the existing spectrum resources are becoming more and more tense,and the frequency of electromagnetic interference will be greatly increased.When FSS is used,the equipment can work better,and the use of FSS with stable angle can further achieve high work efficiency.In this paper,the important characteristics of FSS with angular stability are studied and analyzed in detail,and four FSSs with good angular stability are proposed.The basic theories involved are analyzed,including the multi-frequency characteristics,miniaturization characteristics,broadband characteristics of FSS,and the simplification of the broadband unit structure.The main work of this paper is as follows:(1)Based on the traditional cross-shaped structure and branch folding and bending technology,a multi-frequency FSS structure with stable angles is designed.The unit has a size 0.126?×0.126? and thickness 0.01?.The simulation results show that when the incident angle increased from 0° to 60°,the maximum deviation rate of the unit does not exceed 2%.The actual measurement results show that the proposed multi-frequency FSS structure performs well under different polarization modes,and at normal incident angles,the actual measurement results are basically the same as the simulation results,the trend is the same,and it has good angular stability and polarization stability..(2)In fact that the length of the branches of the FSS unit determines the resonant frequency characteristics,the degree of miniaturization is not very high.For this reason,a technology of loading metal pillars is proposed,and a miniaturized FSS unit structure is designed.A simple comparison is made between the flat FSS without metal columns and the FSS with metal columns.The unit size of the flat FSS is 0.133?×0.133?,but the unit size of the FSS loaded with metal columns is only 0.07?×0.07?.It can be seen that the degree of miniaturization has been greatly improved.When the HFSS simulation is used to analyze the angular stability of the FSS unit loaded with metal pillars,it is found that when the incident angle increases to 75°,the maximum value of the resonant point shift rate is only 0.83%.And its angular stability is further improved,and it has a strong angular stability has achieved.Also the result of miniaturization has achieved..(3)Aiming at the above-mentioned single-screen FSS,which is usually difficult to achieve the filtering characteristics of "flat top and steep cut-off",a three-screen cascade method is proposed to design an FSS unit that can work in the C-band when the incident angle reaches 45°.The circuit method is used to analyze it,and through HFSS simulation,it is verified that the FSS unit can work well in the C frequency band.(4)For the three-screen cascade method,an FSS with a good broadband effect is designed.However,the three-screen cascade is often pressed by two-layer boards.At this time,it is necessary to align the unit structure very accurately.Otherwise,the FSS The filtering effect will produce a large offset or even fail to work within the designed frequency band.To this end,a method of loading the middle layer structure into the upper and lower layers without changing the shape of the original unit structure is proposed.After optimized simulation analysis,the FSS unit structure can still work in the C-band at an incident angle of 45°.Finally,the improved FSS unit is processed.The measured results are the same as the simulation results,and the TM polarization is basically the same.It is verified that the method can not only effectively reduce the structure of one layer,but also makes the processing process simpler and has better results.It has great practical engineering significance.