Study On Reconfigurable And Miniaturized Frequency Selective Surface

Frequency Selective Surface(FSS)is a two-dimensional periodic array consisting of the same metal patch or the same aperture elements on a dielectric substrate.When radiated by electromagnetic wave,the FSS exhibits filtering characteristics: band-stop or band-pass.Therefore,it is used as a spatial filter.The FSS has a wide range of applications,for example,the band-pass type of it can be used as a radome,and the band-stop type of it can be used as a sub-reflector.Based on the background of the applications of FSS,the design principles and analysis methods are researched,and the traditional FSS of single function and large element size is considered as a breakthrough,which leads to the research hotspot of reconfigurable and miniaturized technology,then the reconfigurable and miniaturized frequency selective surfaces are studied in depth.The main contents of the thesis are arranged as follows:1.After learning the basic theories of the FSS,the filtering characteristics of two typical FSS are analyzed by combining the important technical parameters which affect the performance with the analysis methods of FSS.It lays the foundation for the design of reconfigurable FSS and miniaturized FSS.2.In order to solve the problem of the traditional FSS with single function,two FSS elements with reconfigurable characteristics are designed based on the technology of loading diodes.The FSS element is obtained based on the modified classical cross-frame element,and then is integrated with the varactor diodes,realizing the frequency adjustable characteristic.In subsequent research,the PIN diodes take the place of the varactor diodes,and eventually,an element with single dual-frequency switchable function is proposed.3.In order to solve the problem of poor angular stability of the traditional FSS,an element with high angular stability is designed based on the 2.5D closed loop.This thesis firstly researches the methods of miniaturization and studies the principles how metal via achieves the miniaturization of element size,and then proposes a 2.5D closed loop element with high angular stability.The simulated results show good stability for incident angle ranging from 0° to 80°.Based on this structure,an element with high angular stability and miniaturization is obtained by loading a metal patch with slots to reduce its resonance frequency.Finally,the FSS is processed and measured.The measurements are basically in agreement with the simulations,and the validity of the design methods above is verified.4.In order to solve the problem of large element size of the traditional FSS,an element based on the 2.5D closed loop structure is designed in this thesis,which realizes the performance of miniaturization by researching the metal via inside the element.At first,the traditional 2.5D closed loop is chosen as the research object and the metal via inside the element is segmented,and then the middle layer of different structures is introduced.Next,the influence of different middle layers on miniaturizing the size of elements is compared.Finally,a 2.5D closed loop structure with a middle layer of “U” shape is designed,and its element size is reduced to 0.033?.In addition,it is found that the miniaturization of the element size is more obvious with the increase of the number of middle layers introduced.At last,the FSS is processed and measured,and the measurements are in agreement with the simulated results,which prove that the proposed method is feasible to miniaturize the 2.5D FSS element size.