| Frequency Selective Surface(FSS)is a periodic structure composed of a periodic arrangement of metal resonant units,and has selective transmission characteristics for electromagnetic waves irradiated on the surface.Due to the characteristics of its spatial filter,FSS has high application value in the field of electromagnetics.Therefore,research and design of high-performance FSS have always been a hot research direction.This thesis studies some important properties of FSS,including angle-stability,miniaturization and absorption.The main research work of this thesis includes the following aspects:1.The working principle and the main structure of FSS are introduced.The causes of grating lobes and the conditions for avoiding grating lobes are discussed.The influence of some important parameters on the transmission performance is analyzed based on the basic FSS unit.Some empirical rules are summarized,which have certain guiding significance for designing FSS units with specified performance.2.A band-stop FSS with angular stability and improved bandwidth performance is designed.By comparing the performance of some basic units,a square ring element with better bandwidth performance and angular stability is selected as the primary structure,and the bending deformation is performed to improve the angular stability of the unit.Then metallized vias are introduced to improve the bandwidth.Using the equivalent circuit method,the resonance principle of the FSS unit is analyzed by a set of empirical formulas for calculating the equivalent circuit.The simulation results show that the resonance frequency of the FSS unit can be maintained at around 0.73 GHz when the incident angle of TE and TM polarized electromagnetic waves ranges from 0° to 85°.Compared to the primary structure,the relative bandwidth increased from 21.2% to 61.2%.The FSS of this design is processed and tested.The test results are in agreement with the simulation results,indicating that the FSS has good angle stability and bandwidth characteristics.3.A miniaturized dual-band bandpass FSS has been designed.By bending a metal strip of a FSS unit in the surface of the dielectric layer,the current path is increased and miniaturization is obtained.Then metallized vias are introduced to further increase the current path and miniaturization.At the same time,the introduction of the metallized vias adds a new resonance point at a high frequency,realizing the dual band pass effect.The simulation results show that the FSS unit of this design has two resonance points in the 1-10 GHz frequency band: 2.7 GHz and 7.2 GHz,and the cell size is 0.045?(where ? is the wavelength corresponding to the low frequency resonance frequency),achieving good miniaturization.4.A broadband absorptive FSS with miniaturization effect is designed.A broadband absorbing theory and a corresponding absorptive FSS unit are introduced.The important parameters are analyzed,and their effects on the resonant frequency and absorbing bandwidth are summarized.Based on these analysis,an new unit is designed by adding a resonant structure to the absorptive FSS unit,which further expands the bandwidth.The miniaturization method of the absorptive FSS unit is studied,and a miniaturization method is proposed.According to this method,an miniaturized absorptive FSS unit is designed.The simulation results show that the absorbing bandwidth of the miniaturized absorptive FSS unit reaches 145%,and the length is reduced by 35% compared to the absorptive FSS unit. |
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