Design Of Multiband Double-layer Frequency Selective Surface Absorber

Frequency selective surface(FSS)is a new type of absorbing material which has the characteristics of light weight and wide bandwidth.Double-layer FSS has the advantages of absorbing waves simultaneously in different wavebands.In this paper,we design a absorber body which produces wave absorbing effect in L,S and X-band.The specific research is as follows:The absorption mechanism of single-layer FSS in X-band is studied.The structure of the model and the effect of the pattern are analyzed,and the influence of various parameters is studied.The equivalent parameter values of the structure are analyzed by equivalent transmission line theory.Each equivalent parameter is analyzed by changing the size.In addition,the Smith chart is used to analyze the overall structure and the effect of each layer.Finally,each parameter value was be optimized in order to get the best absorber in the X-band.And the X-band optimized design method is applied to the L and S bands.A broadband absorber with a reflectivity of-10 dB at L and S wavebands is obtained.The absorber can achieve the desired effect in the L,S-band and X-band respectively.On this basis,a new type of absorber is designed.This paper adopts double-layer FSS as the realization method of the new type of absorber.The wave absorber can achieve full coverage of the reflectivity-10 dB in the X-band,and the L and S band absorbing effects are taken into consideration as much as possible.For the double layer FSS,the influence of upper and lower layer placement,interlayer coupling and the superposition design on the overall performance was analyzed.By studying the transmission of the single-layer pattern,we decided to place the pattern with absorbing effect in the X-band on the upper layer and the pattern with the absorbing effect in the L and S-band on the lower layer.Finally,a broadband absorber with a reflectivity of-10 dB at 1.3-4 GHz and 8-12 GHz isobtained through the simulation of the final two-layer FSS model.The correctness of the model is proved by experiments.