Research And Design Of Ultra-Wideband Frequency Selective Absorber Based On Metamaterial

With the development of modern radar detection technology,more and more weapon systems and communication systems begin to apply the technology to the enemy detection function.In this case,radar stealth technology,as a means to avoid the discovery of its own facilities by the enemy,has increasingly high strategic value.In addition,in today’s highly developed information technology,electromagnetic interference in the environment will also affect the normal operation of communication equipment,so the shielding and elimination of useless signals has become a research hotspot.The frequency selective surface has been used to eliminate electromagnetic interference and achieve radar stealth for a long time.The band-pass frequency selective surface,preventing irrelevant signals from entering,can realize the reflection of out-of-band signals and the transmission of in-band signals.However,there is another problem that bandpass frequency selective surface can only reduce the monostatic radar cross section.In order to reduce the radar cross section of the multistatic radar,people have designed a frequency selective absorber with more complex functions.Frequency selective absorbers can be divided into two categories.One is the rasorber proposed earlier,which is characterized by band-pass in the antenna frequency band and electromagnetic wave absorption rather than reflection outside the band to ensure the reduction of multistatic radar cross section.It can also be used as a radome.The other one is the research and design target of this paper.The antenna is characterized by band-stop reflection in the frequency band and absorption out of the band,which can be used as a substitute for the metal grounding plate of the antenna.However,this kind of frequency selective absorber was put forward late.Most of the current designs have only one reflection band,and the position of the reflection band cannot be adjusted,which greatly limits the application prospects of the frequency selective absorber.In order to solve these problems,two types of frequency selective absorbers are proposed in this paper.While possessing ultra-wide absorption band,the position of reflection band can also be adjusted by adjusting physical parameters or loaded DC voltage,which can be combined with multi-band antenna to reduce its radar cross section.The specific work is as follows:The first type of frequency-selective absorber consists of a lossy layer and a lossless layer.The lossy layer is the absorber that realizes the broadband electromagnetic wave absorption.The lossless layer is the bandstop frequency selection surface that generates two reflection bands in the absorption band.Both reflection bands can realize their independent adjustment by changing the physical parameters of the lossless layer structure.The absorption band of the frequency selective wave absorber is from 4.56 to 19.657 GHz,reaching 12.1 GHz.The width of the two reflection bands is about 1GHz,with almost no insertion loss and high selectivity.After unit simulation,we carried out array simulation and physical performance test in turn.At last,we analyzed the array simulation results and physical performance test results.The second frequency selective absorber is improved on the basis of the first one,and its function is further optimized.The adjustment of the frequency of the two reflection bands is controlled by the capacitance value of the introduced varactor diode.Therefore,the key to the design of this frequency selective absorber is that the frequency response of the frequency selective absorber will not be interfered by the DC feed line,resulting in the distortion or deterioration of the frequency curve,which requires consideration of the difficulty,advantages and disadvantages of adopting independent feed line or integrated feed line design.After completing the unit simulation,we also conducted the array simulation and analyzed the results.In this paper,two types of reflective frequency-selective absorbers which can be used for multi-band antennas are designed based on previous theories.These two types of frequency selective absorbers have ultra-wide absorption band and two independently adjustable reflection bands.The difference is that one is passive and the other is active,that is,the adjustment of reflection band frequency is realized by changing the physical structure parameters and the reverse bias voltage at both ends of the varactor diode.After the design is completed,the simulation results are analyzed,and the passive frequency selective absorber is farbicated and the test results are analyzed.