The Research On Frequency Selective Surface With Quasi-Elliptic Bandpass Response

With the rapid development and application of wireless communication technology,the utilization rate of spectrum continues to increase,resulting in an increasingly complex electromagnetic environment.Due to the filtering characteristics for plane electromagnetic waves of different frequencies,polarizations and incident angles,Frequency Selective Surface(FSS)has been widely applied in anti-electromagnetic interference,electromagnetic compatibility,anti-electromagnetic radiation and so on.Improving frequency selective performance is usually one of the research focuses in the design of FSS.After the in-depth study of the basic principles,performance influencing factors and related analysis methods of FSS,five quasi-elliptic bandpass FSS are proposed in this paper.The main research contents are as follows:(1)A bandpass FSS based on coupled ring resonators is proposed.Two transmission poles and three transmission zeros are introduced by using the electromagnetic coupling between ring resonators and the resonance characteristics of square ring resonators.And the frequency selective characteristics and out-of-band suppression of the FSS are effectively improved.Moreover,the working principles of the FSS is analyzed and discussed with the aid of an equivalent circuit model.Then,the relevant influence parameters of FSS are analyzed with electromagnetic simulation software CST.The equivalent circuit model and full-wave simulation results verify the feasibility of the design.(2)A bandpass FSS based on stubs-loaded ring resonators(SLRR)is proposed.Firstly,a method by using transmission line models to calculate the resonant frequency of SLRR under normal incident wave is proposed.And the method can be extended to the calculation of any other symmetrical branch-loaded resonators.Then,an equivalent circuit model is established to investigate the operating mechanism and the cause of transmission zeros of the proposed FSS.Hereafter,the key parameters of FSS were swept to summarize the influence characteristics of structural parameters.Finally,a FSS prototype based on the proposed design structure was fabricated and assembled.And the prototype was measured in a semi-open environment.Good agreements between the measurement results and the simulation results verifies the correctness of the proposed structure.(3)Two bandpass FSSs(FSS I and FSS II)based on the antenna-filter-antenna model are proposed.Firstly,the design structure of FSS I is introduced.And the resonant frequencies of the antenna parts in the FSS I structure are calculated with the cavity mode theory analysis.Then,the working princiles of the FSS I is investigated and discussed with the aid of simulation software.Based on the design of FSS I,the design of FSS II is achieved by changing the structure of the filter part.Additional transmission poles and zeros are introduced,which effectively improves frequency selective performance and out-of-band roll-off characteristics.Simulation results show that FSS I and FSS II exhibit excellent quasi-elliptical frequency response and frequency stability,and have vital research and application value.(4)A three-dimensional(3-D)FSS based on circular waveguide structure is proposed.And the working principle of the 3-D FSS is researched from the aspects of structural analysis,simulation results and parameter scanning.The simulation results show that the 3-D FSS possesses a good quasi-elliptical frequency response at normal incidence.Finally,a prototype was processed and tested to verify the effectiveness of the design.