The Research And Design Of The Frequency Selective Rasorber

In modern high-tech warfare,the stealth and anti-interference of the aircraft are important for improving the survivability and assault ability.The antenna of the aircraft is not only a detection source,but also a scattering source.The reduction of the radar cross section(RCS)of the antenna system is an important subject.The frequency selective surface(FSS)are widely loaded in radomes.In the operating band of an antenna,EM waves can pass the FSS.Outside this band,the EM waves are reflected.The reducing of the scattering in the main threat direction makes it difficult for the mono-static radar to receive the radar echo and increase the anti-interference of antenna system.With the developments of bistatic and multistatic radars,FSS radomes have been unable to meet the stealth requirements of the antennas.Scattered waves that are difficult to receive by mono-static radar can be received by bistatic and multistatic radar located at different locations.In this paper,a variety of frequency selective rasorbers(FSR)are proposed.FSR combines the FSS and absorber.FSR ensure the signal transmission of the antenna in certain frequency bands while absorbing out-of-band waves emitted by the enemy,so that the bistatic RCS is reduced.Due to its absorption and transmission characteristics,the FSR has a significant advantage over conventional FSS in bistatic and multistatic RCS reduction.The main work of this paper is as follows:A bandpass FSR based on split ring resonators(SRR)is first proposed in this paper.The lossy layer is improved by a single-polarized dipole absorber and a SRR.By combining with the FSS,the structure achieves one absorbing band on each side of the transmission band.To understand the mechanisms of transmission,reflection and absorption,the surface current distribution of the structure is studied.The RCS reduction performance of the FSR is investigated by comparing the RCS of FSS and FSR.Finally,A prototype is fabricated and measured.The results show that the center frequency of the passband is 5.74 GHz with an insertion loss of 0.25 d B.The lower and higher absorption bandwidths with absorption coefficient higher than 80% range from1.92 to 3.73 GHz and from 7.41 to 9.34 GHz,respectively.The relative bandwidth of refection band with refection coefficient less than-10 d B is 130.5%.Secondly,FSRs with multi-loop are modeled,analyzed and experimentally verified.Based on the equivalent circuit model(ECM),the FSRs based on Minkowski loops and the folded loops are designed.The FSR based on Minkowski loops is bandpass.The simulation results show that the structure has a passband with an insertion loss of 0.36 d B at 7.66 GHz.Additionally,the fractional bandwidth of-10 d B reflection reaches up to 115.7% under normal incidence.On the basis of FSR based on Minkowski loops,a FSR with two passbands and two absorbing bands based on folded loops is designed to realize RCS reduction and anti-interference of dual-band antenna system.The FSR realizes two transmission poles at 6.2 GHz and 10.3 GHz,respectively.The relative bandwidth of refection band with refection coefficient less than-10 d B is 111.4%.The lower and higher absorption bands with absorption rates greater than 80% range from3.45 to 4.8 GHz and 7.55 to 9.1 GHz,respectively.Finally,the graphene-based terahertz FSR is explored and proposed.Two absorption bands are realized by surface plasmon resonance,and FSS is loaded on the substrate to achieve transmission response.The simulated results indicate that it is almost transparent to incident waves below 0.19 THz and between 1.3 and 1.67 THz with a center frequency of 1.49 THz.Meanwhile,there are two absorption bands ranging from 0.54 to 0.84 THz and 2.13 to 2.29 THz.Moreover,the absorption rate and bandwidth of the absorbing bands can be tuned by the chemical potential and relaxation time of graphene.