Research On Stability Of Ultra-Wideband Frequency Selective Surface

With the tendency towards the higher frequency and the wider band of communication systems,the research on ultra-wideband(UWB)frequency selective surface(FSS),which is widely used in the antenna stealth and electromagnetic shielding,is increasingly developed.In the design of an ultra-wideband FSS,it is difficult to maintain the stability in different incident angles and polarizations.For improving the stability of ultra-wideband FSS,the miniaturization method is used to suppress the resonance frequency shift caused by the changes of the angle and polarization of electromagnetic waves.By studying designs of the fractal patches,the parasitic patches and the 2.5D metallic vias,the effect of miniaturization on the stability of ultra-wideband FSS is proved.This paper is proposed to solve the problems of poor stability of ultra-wideband FSS.The main works and innovations of this paper are as follows:(1)Based on the study of multi-level cascaded structure,the ultra-wideband FSS unit with the Minukovski fractal patches and Koch fractal patches is proposed,and the unit size relative reduction of 33.3% is realized by the self-similarity of the fractal structure.Compared with the original structure,the fractal design ultra-wideband FSS achieves an average 52.0% reduction of the resonance frequency deviation when the electromagnetic wave enters at 60 °,and the relative bandwidth of the structure is 89.9%.It turns out that the miniaturized design based on the fractal design enhances the stability of the ultra-wideband FSS.(2)Based on the research of multi-level cascaded structure,for the first time,the parasitic patches are loaded in the capacitor-inductor-capacitor ultra-wideband FSS unit cell to provide additional coupling,and the miniaturization can be achieved.When the incident angle is 60 °,the average suppression of the resonant frequency deviation due to the loading of parasitic patches reaches 74.3% and the relative bandwidth of FSS is also increased to 109.4%.The measured results are in good agreement with the simulations.It is verified that the miniaturized design based on the parasitic patches enhances the stability of the ultra-wideband FSS.(3)Based on the research of planar ultra-wideband FSS,the planar hexagonal rings arranged in a honeycomb pattern are arranged in the upper and lower layers alternately and connected by the 2.5-dimensional metallic vias,then the ultra-wideband FSS consists of miniaturized hexagonal rings is realized.The ultra-wideband FSS with 2.5-dimensional metallic vias design is superior to the original planar structure in terms of Transverse Electric(TE)and Transverse Magnetic(TM)polarizations,the reduction of resonant frequency deviation is 66.7%,the relative bandwidth is 121.6%,the polarized sensitivity is very low in the whole working bands,and the measured results are in good agreement with the simulations.It is verified that miniaturization design based on the 2.5-dimensional metallic vias improves the polarized independence of the ultra-wideband FSS.