Research On UWB Absorptive/Transmissive Frequency Selective Surface

With the continuous progress of radar detection technology,improving the stealth performance of our combat equipment is facing great challenges.The antenna is one of the main factors affecting the radar cross section.Absorptive/transmissive frequency selective surface(ATFSS)has the integrated characteristics of in-band transmission and out-band absorption,which has great value in the field of stealthy radome.On the premise of ensuring the normal operation of the antenna,it can realize the normal transmission of signals within the working passband and absorb the electromagnetic waves outside the working band to achieve the bistatic RCS reduction in the whole space and improve the omnidirectional stealth of the antenna.This thesis mainly focuses on the absorptive/transmissive frequency selective surface(ATFSS),a lossy impedance surface and a lossless bandpass frequency selective surface are designed,and then composite simulation optimization is carried out to design an absorptive/transmissive frequency selective surface with the absorption band below the transmission band.Firstly,a lossy impedance surface based on the principle of circuit analog absorber is designed,and the metal strips on both sides of the dielectric plate are connected by introducing metallized vias to achieve miniaturization.When the lossy structure is loaded on the metal floor,the bandwidth with the absorption rate greater than 80% is 2.29-4.85 GHz,and the insertion loss of the lossy structure without the metal floor is less than 1.2d B at 5.4-18 GHz,which has good polarization stability and angular stability.The measured results are in good agreement with the simulation results.Secondly,by using a multi-layer cascaded non-resonant structure,a band-pass frequency selective surface composed of three layers of metal rings,metal grids and metal rings is designed to achieve ultra-wideband characteristics.The transmission passband with insertion loss less than 1d B is 6.4-19.3GHz,the relative bandwidth is 100.4%,and it has good polarization stability and angular stability.The measured results are in good agreement with the simulation results.Finally,the composite simulation of the designed loss layer and the FSS layer is carried out,and an absorptive/transmissive frequency selective surface is designed.The bandwidth with the absorption rate greater than 80% is 2.3-3.9GHz,and the transmission passband with insertion loss less than 1d B is 6.2-19 GHz,the relative bandwidth is 101.6%,and it has good polarization stability and angular stability.The measured results are in good agreement with the simulation results,and the monostatic RCS reduction in the range of 2.5-3.9GHz is not less than 5dB,and the maximum reduction is 8dB.