Research On 3D Frequency Selective Surface With Wide Band And Multiple Bands

Frequency selective surface(FSS)is a spatial filter that has frequency selection characteristics for electromagnetic waves with different operating frequencies,polarization states and incident angles.It is widely used in modern antenna and microwave communication systems.The traditional two-dimensional(2D)FSS can be realized by printing a metal patch on a dielectric substrate or etching an aperture structure on a metal plate.However,it is difficult to achieve high-quality filtering performance due to the limited working mode,such as high selective filtering performance,frequency selective absorption performance and multi-band characteristic.The new three-dimensional FSS is composed of three-dimensional(3D)unit structure arranged in the periodic plane.Due to its unique cavity structure,it can excite multiple resonant modes or construct multiple resonators,making it easier to generate multiple transmission poles or zeroes,which makes it easier to achieve high quality filtering performance.Thus,this thesis adopts stacked slotline unit and rectangular waveguide loading slotline unit to realize bandpass FSS with wide suppression band,transmission(reflection)-microwave absorbing FSS and multi-band FSS,and the specific research contents are as follows:(1)This thesis introduces the research background and basic concepts of FSS firstly.Then,this thesis compares the traditional 2D FSS with the new 3D FSS from the framework and working mechanism of the structure.Finally,we introduce the common analysis methods of FSS,and introduce the application of equivalent circuit method in FSS design with metal strip structure and stacked microstrip structure as examples.(2)In terms of high selectivity filtering performance,this thesis implements a bandpass FSS with broad stopband performance based on the stacked slotline unit.Firstly,the working mechanism of the uniform stacked slotline structure is introduced,and the corresponding equivalent circuit model is established.Secondly,according to the proposed equivalent circuit model(ECM),the design process of bandpass FSS with wide suppression band is described,which was processed and tested.The tested results were in good agreement with the simulation results.(3)In terms of frequency selective absorption performance,the transmission-microwave absorbing FSS is designed by using the slotline cell unit.The working mechanism is deeply analyzed and the dual-polarized transmission-microwave absorbing FSS structure is processed and the measured results are in good agreement with the simulated results.Secondly,based on the transmission line circuit model design,the reflection-microwave absorbing FSS structure is realized by stacked slotline structure,and the full-wave simulation results are in good agreement with the equivalent circuit results.(4)In terms of multiband performance,this thesis proposes a tri-band bandpass FSS.Firstly,a stepped slotline structure A is longitudinally loaded in a rectangular waveguide to realize a bandpass FSS with a wide suppression band.Secondly,on the basis of the implemented bandpass FSS with wide suppression band,the slotline structure B is continuously loaded to implement a dual-band bandpass FSS.Then,on the basis of the implemented dual-band bandpass FSS,the slotline structure C is continuously loaded,thereby implementing a tri-band pass FSS structure.Finally,according to the designed physical parameters,the above three kinds of FSS are processed and tested.Due to the problem of the rectangular waveguide processing method,the tested results show that large insertion losses are achieved.So the rectangular waveguide needs to be improved.