Research And Design Of Frequency Selectivesurface Based On The Equivalent Circuit Model

The frequency selective surface is a two-dimensional periodic structure with spatial filtering characteristics.The FSS can be divided into the series resonance FSS and the parallel resonance FSS.As the planar structure with filtering characteristics,FSS is often used for radomes,electromagnetic shielding layers,and radar absorbing materials.With the increasing integration and miniaturization of various types of antennas and communication devices in recent years,as part of the entire communication system,the miniaturization requirements of FSS have also increased.At the same time,The miniaturization can reduce the dependence of FSS on periodic boundary conditions in engineering applications.Specifically,it reduces the proportion of cells affected by edge current reflection in the total cell.In addition,the increase in the application of multifrequency devices has also driven the development of multi-frequency FSS.The main achievements of this thesis are as follows:Firstly,the development history of frequency selection surface and the research status of domestic and foreign countries are briefly described.After introducing the basic working mode of FSS,this thesis analyzes the four basic resonance modes of FSS.Next,this thesis analyzes several types of parameters that affect the performance of FSS and aims to provide some guidance for the initial design and subsequent optimization of FSS.The thesis briefly introduces several FSS analysis methods and commercial simulation software and focuses on the analysis,modeling and optimization methods of the equivalent circuit method.The advantages and current shortcomings of the equivalent circuit method in analyzing and optimizing FSS are introduced in detail.Subsequently,the actual test environment and test steps of FSS are introduced.Then,the main means of miniaturization of FSS is analyzed and summarized.This thesis mainly analyzes the simulation results based on the broadband equivalent circuit.Then the FSS performance optimization scheme is proposed according to the constructed broadband equivalent circuit.In the analysis of the working principle of the hook FSS,the modeling steps of the broadband equivalent circuit are introduced in detail.This laid the theoreticalfoundation for the subsequent equivalent circuit analysis of FSS.By optimizing the traditional parallel plate capacitor structure,this thesis proposes a spiral capacitor structure with larger equivalent capacitance.A bandpass FSS and a bandstop FSS were constructed using spiral capacitor structures.The analysis results demonstrate the stability of the spiral capacitor structure performance in different types of FSS.Both FSS models have high miniaturization,low profile,and good angular stability.Finally,this thesis solves the problem of equivalent circuit modeling of FSS when the main polarization structure and the cross-polarization structure are strongly coupled with each other,and proposes a new equivalent circuit modeling method.Subsequently,the principle of equivalent structure boundary division was optimized according to the new modeling method.The interaction between the equivalent capacitor structure and the equivalent inductor structure is discussed.Based on this,the spiral inductor FSS is designed.The type of equivalent capacitor in the spiral inductor FSS is the coplanar capacitor rather than the interlevel capacitor.Therefore,the energy loss in the FSS unit is lower than in the FSS in the foregoing.