Investigation Of Compact Dual-Band And Reconfigurable Frequency Selective Surface

Frequency selective surface(FSS)is a two-dimensional structure of single-layer or multilayer which is periodically arranged of identical elements,and this structure can transmit or reflect electromagnetic wave of particular polarization,incident angle and frequency.Because of its special filtering characteristics,FSS is often used in radar stealth technology,satellite communication,electromagnetic compatibility and many other aspects.For the characteristics of the traditional passive FSS can not be changed after the design,it can not meet the changeable requirements in practical application.Therefore,the concept of reconfigurable frequency selective surface(RFSS)is proposed on the basis of traditional passive FSS.In this thesis,the basic theory of FSS and the common design principle of highperformance FSS are studied and analyzed.Focusing on the dual-band,miniaturization and reconfiguration of FSS,the main work of this thesis is as follows:Firstly,the basic concept of FSS are briefly introduced,and the general rules of the influence of the basic parameters of FSS are summarized.The causes and conditions of grating lobe are analyzed in principle,which guides the design of FSS to avoid the occurrence of grating lobes.This thesis introduces several theoretical analysis methods of FSS and their respective usage scenarios.Taking the typical FSS structure as an example,the equivalent circuit analysis method is established to analysis the performance of the unit,which lay the foundation for studying the working principle of high performance FSS.Secondly,the traditional cross-type aperture and square aperture are combined in the same unit through a staggered composite method to achieve the performance of dual-frequency resonance.By analyzing the field distribution at resonance,an equivalent circuit model is established for the unit to analyze the working principle of the unit.Then,the miniaturization of this dual-band FSS is realized by using new type of bending structure.By analyzing the resonance principle of this bending structure,a high performance FSS is optimized.The final design can provide two closely spaced pass-bands at 1.05 GHz and 1.49 GHz,and the ratio of two resonant frequencies is as low as 1.42.The size of the miniaturized FSS is as small as is 0.039l ?0.039l.The performance of the proposed FSS remains stable under the oblique incidence(up to 75°)and different polarizations.The optimized dual-band and miniaturized FSS is processed,and the measurement in microwave chamber are consistent with the simulation results,which proves the correctness of simulation results.Finally,introduce the common classification methods of RFSS and summarize the implementation methods of tuned RFSS and switched RFSS.After analysing the shortcomings of current implementations of switched RFSS,the thesis proposes a new-type implementation of switched RFSS.Then,on the basis of the cross-shaped structure,a switchable RFSS with self-complementary structure is designed by bending structure and loading PIN switches between cells.The unit has certain miniaturization characteristics,and the performance of FSS can be changed to bandpass or bandstop in both frequency bands by controlling the excitation.In order to realize a wider band of radar cross section reduction when this RFSS is applied to radome,the switchable RFSS is cascaded with a dual passband FSS by the air chamber to expand the bandwidth of stop band without affecting the characteristics of the pass band.After cascading,the bandwidth of stop band is up to 250% compared with the original RFSS,and the edge steepness of the pass band is improved.The suitable PIN switch is chosen for the RFSS,and RFSS unit itself can be used as the PIN switch's bias circuit.Finally,a simple and effective bias circuit is designed for the RFSS unit,and the designed RFSS is processed.The test results are consistent with the simulation results,which proves the feasibility of the simulation experiment.