Research And Design Of Reconfigurable Frequency Selective Surface

Reconfigurable frequency selective surfaces(RFSSs)have important applications in electromagnetic shielding,electromagnetic compatibility,stealth radome and other fields due to their active adjustable electromagnetic characteristics.Therefore,the research on highperformance RFSS has practical engineering significance.There are two kinds of RFSS.One is tunable RFSS,the other is called switchable RFSS.Different functions are suitable for different application scenarios.This paper carries out research and design for switchable RFSS.The main work contents and innovations are as follows:1.Design and fabrication of the broadband switchable transmission/reflection RFSSFirstly,the equivalent circuit parameters of PIN diode were studied,and a test system was established based on microstrip line to extract the actual equivalent circuit parameters of diode,so as to improve the accuracy of subsequent RFSS design modeling.On this basis,this paper proposes two kinds of switchable transmission/reflection RFSS,which are the multi-layer structure fed in parallel and the single-layer structure fed in series.The multi-layer RFSS is composed of two FSS with the same element shape and orthogonal direction connected through the air layer.By observing the current distribution of the structure at the resonant point,the equivalent circuit model is established and its working mechanism is studied.The simulation results show that the switching bandwidth of the above structures are great than 20% in both TE and TM polarizations with the incident angle up to 45°.Considering the machining difficulty and cost,the single-layer RFSS was finally processed and tested,and the measured results are consistent with the simulated results.2.Design and fabrication of the broadband switchable absorbing/reflection RFSSFirstly,the basic theory of absorber is studied,and the calculation method of absorption rate and impedance matching principle are analyzed emphatically.Then,according to the noncoplanar design principle,an absorbing/reflecting RFSS structure was innovatively proposed by combining the transmission/reflection RFSS designed above with the absorber,and the working mechanism of the structure was further analyzed by observing the current distribution.The simulation results show that the switching bandwidth of the proposed structure is great than40% in both TE and TM polarizations with the incident angle up to 45°.Finally,the structure is fabricated and tested,and the test results are consistent with the simulation results.Compared with the structures in the existing literature,the proposed structure not only realizes broad switching bandwidth,but also has the advantages of good stability of angle and polarization.Compared with the RFSS of the same type in the existing literature,the switchable transmission/reflection RFSS and switchable absorption/reflection RFSS proposed in this paper have the advantages of wide switching bandwidth,wide Angle domain and double polarization.