Research On Miniaturized Multi-frequency Reconfigurable Frequency Selective Surface

Frequency Selective Surface（FSS）is an artificial electromagnetic structural material that can effectively control electromagnetic scattering.It has a wide range of applications in the fields of electromagnetic stealth,satellite communication and electromagnetic compatibility of electronic equipment.With the continuous development of the information industry and the continuous expansion of wireless spectrum resources,the miniaturization,multi-band and reconfigurability of the frequency selective surface are particularly important in engineering applications.This thesis focuses on these important properties,and designs a new ultra-miniaturized FSS loaded with metal vias,a dual-band miniaturized FSS with complementary structures,a tri-band FSS based on resonance and coupling mechanisms,and a broadband reconfigurable FSS with polarization stabilization properties.The main work and innovations of the thesis are as follows:1.In order to solve the shortcomings of traditional FSS with large size and high profile,a rotationally symmetric miniaturized and low profile FSS is proposed.The FSS unit is composed of convoluted dipoles,and the hexagonal elements are arranged obliquely to form a compact FSS,which avoids the generation of grating lobes,and ensures the incident angle and polarization stability of the proposed FSS;To further reduce the size,the similar patterns are etched on both sides of the substrate,and the two metallic layers are connected by vias.By iteratively increasing the layers and metallic vias,ultra-miniaturized performance is achieved.The size of the miniaturized FSS is only0.02λ₀×0.02λ₀,and it maintains a stable transmission response under a wide range of incident angles from 0°to 60°.The measured results are the same as the simulation results.2.Using complementary coupling technology,a dual-band miniaturized FSS with independently adjustable frequency bands is designed.The passbands are located at 2.15GHz and 3.8 GHz,respectively,and high out-of-band rejection is obtained.These two bands can be tuned simply and flexibly.It exhibits highly stable characteristics in different incident angles and polarizations,and its size in the low frequency band is only0.05λ₀×0.05λ₀.In addition,a tri-band miniaturized FSS is designed in the form of multi-layer cascade for the millimeter-wave frequency band.The coupling effect and resonance effect between the layers produce highly selective pass-bands at 20 GHz,28 GHz and 38GHz,respectively.Pass-band insertion loss is maintained within 0.5 d B,and stable transmission response is maintained in the range of 0°-60°incident angle.The measured results of the two FSSs are in good agreement with the simulation results.3.A diode-based broadband reconfigurable FSS is designed.By constructing miniaturized ring slot resonators on the top and bottom layers,and utilizing the coupling effect of the middle inductive layer,a broadband response is formed.The bias network is researched and optimized,and the integration of bias network and the structure can effectively avoid interference of bias network to the transmission performance.orthogonal placement of PIN diodes in the ring slot realizes the switching of passband and stopband from 4.2 GHz to 5.0 GHz.The passband has the characteristics of flat top and steep drop,and the stopband attenuation can reach 45 d B.Replacing the PIN diode with a varactor diode enables tunable performance in the frequency band from 2.17 GHz to 4.8 GHz.The proposed broadband reconfigurable FSS achieves polarization stability and the physical processing and testing of the reconfigurable FSS based on loaded PIN diodes has been carried out to verify the feasibility of the scheme,which expands the application scenarios of reconfigurable FSS.