Design Of Absorber Based On Polarization-insensitive Broadband Tunable FSS Pattern

In today's battlefield,stealth technology is a highly valuable military application technology,getting more and more attention in recent years.The study of absorbing materials also becomes a hotspot.Frequency selective surface(FSS)absorber is a kind of structural absorber.In this paper,three types of frequency selective surface(FSS)absorbers were studied for different applications circumstance.These three kinds of absorbers are respectively applied to different occasions.These three kinds absorbers all have good performance in the low frequency,broadband,and polarization-insensitive characteristics.Firstly,the simulation of FSS absorber,the measurement and the theory of transmission line model are introduced.Establishing the equivalent transmission line model of the Salisbury screen proves the reliability of the transmission line model analysis method.And the absorption mechanism of the FSS absorber is analyzed by discussing the impedance matching of the transmission line.A polarized-insensitive wideband continuously adjustable FSS absorber was designed for the 1 GHz-8 GHz band.The parasitic parameters of tunable devices in the active tunable absorber are determined by fitting method,which reduces the difference between the simulation and measurement and helps the design with more accurate simulation.Finally,the parasitic capacitance of the PIN diode is 0.05 pF.Through the electric field distribution and electric current field distribution,the causes of two absorption peaks with single resistance were analyzed.The peak at the low frequency is generated by magnetic resonance and the peak at the high frequency by electrical resonance.In addition,the transmission line model analysis shows that the electric field distribution is varied,as the resistance increases,meaning that different parts of pattern work so that the corresponding equivalent inductance and capacitance values are different,leading to the movement of resonant peak.According to the oblique incidence simulation and measurement results,the design of the adjustable absorber is shown with good stability in the range of 45~o.In order to make the absorber adjusted to environments where external excitation can not be given and keep low frequency performance,a passive double-layer FSS absorber for 1-8 GHz was designed based on the FSS pattern of active tunable absorbers.The additional single ring FSS layer on the top of original pattern not only demonstrated that the multilayer is an effective way to achieve a multi-peak wide band,but also improved the performance of the intermediate band 3 GHz-7 GHz with a reflection coefficient of 1.5GHz-8 GHz to-8 dB.Finally,to achieve the target of thinness and light quality of absorber,two designs with the required 3.15 mm thickness were given for the 2 GHz-6 GHz band in the paper.The first design was to achieve absorption of-6 dB at 2.7 GHz-6 GHz,with a preferred frequency of 3 GHz-4.5 GHz.Another one was at-6 dB in the 2 GHz-6 GHz band;but3 GHz-4.5 GHz was just to-6 dB;the performance of 2 GHz-3 GHz was better.So the correct design was chosen according to the specific using band.