Research On Electromagnetic Metamaterials And Their Applications In Antenna RCS Reduction

With the rapid development of radio technology and radar detection technology,the traditional weapon platforms can no longer meet the operational needs of modern military fields.Thus,stealth technology has attracted much attention as an effective method to improve the capability in combat and survival of weapons.Stealth technology is also called “low detectable technology”.Radar cross section(RCS)is the key concept in radar stealth technology.As an indispensable external equipment in the combat weapon platform,how to reduce the radar cross section of the antenna has become a research hotspot in recent years.As a special scatterer,antenna needs to satisfy specific radiation characteristics.How to realize its low detectability while ensuring the normal operation of it is the key.There are many kinds of stealth technologies to realize the RCS reduction of antenna and loading electromagnetic metamaterials is one of them.Electromagnetic metamaterial is a kind of artificial material.It has the electromagnetic modulation characteristics which the natural materials don’t have.As one kind of the electromagnetic metamaterials,metamaterial absorber(MA)has the absorbing property which is realized by using metamaterials.Metamaterial absorber overcomes the shortcomings of the traditional absorbing materials and achieves better performance which lead to its wide application prospect.Therefore,this thesis has the research on frequency selective rasorber(FSR)and its application based on the above background.In this thesis,firstly,a summarization on RCS reduction of antenna,research background and research status of electromagnetic metamaterials at home and abroad is given.Secondly,the relevant theoretical basis is introduced and the principle of FSR is expounded.Based on relevant theoretical guidance,this thesis designs four kinds of FSR that can meet different application scenarios.One of them is applied to patch array antenna realizing good RCS reduction.The specific contents are as follows:1.Two kinds of FSR with single polarization are studied and designed.The first one is a FSR with one passband and single polarization.The structure realizes the one passband using two LC series resonance circular structure on lossy layer and a square slot on lossless layer.The lumped resistances on lossy layer achieve absorbing property.The passband is at 10.3 GHz and the insertion loss is only 0.26 d B.The relative bandwidth with reflection coefficient lower than-10 d B can reach 114%.The second one is a FSR with two passband and single polarization.Based on the first one,this one adds another LC series resonance structure on lossy layer.Meanwhile,the lossless layer consists of two slot structures.This one can realize two passbands and good absorbing property.The two passbands are at 10.8 GHz and 25.5 GHz with insertion losses of 0.08 d B and 0.1 d B.This two FSRs realize wideband RCS reduction compared with metal ground of the same size.2.Two kinds of FSR with dual polarization are studied and designed.The first one is a FSR with one passband but dual polarization.The lossy layer consists of four metal square rings with stubs,which are connected by a rhombus metallic strip inserted with four resistors.The lossless layer is a simple square slot.This structure is centrosymmetric and realizes dual polarization.The passband is at 5.2 GHz with an insertion loss of 0.3 d B.It can achieve good two-sided absorbing property.The second one is a FSR with two passbands and dual polarization.Compared with the first one,the lossy layer of this one adds another stub into the square ring realizing the second passband.The lossless layer consists of two square slots.The two passbands are at 8 GHz and 11.9 GHz.The insertion losses are 0.39 d B and 0.64 d B under TE polarization,0.40 d B and 0.66 d B under TM polarization,respectively.The band with reflection coefficient lower than-10 d B covers 5 GHz to 12.8 GHz.These two FSRs both realize good RCS reduction compared with metal ground of the same size.3.The designed FSR with one passband and dual polarization is combined with 2×2 patch antenna array realizing the application of FSR on antenna RCS reduction.With the loading of designed FSR on patch antenna array,the antenna array can achieve good radiation characteristic by keeping the transmission band of the metamaterial the same as the operating band of the antenna array.Compared with the original antenna array,the gain in the maximum direction of the array with metamaterial only decreases by 0.36 d Bi.Meanwhile,the RCS of the antenna achieves the minimum values of low frequency band and high frequency band at 4.1 GHz and 6.7 GHz,respectively.Compared with the antenna without metamaterial,it achieves good RCS reduction in the corresponding absorbing frequency band of the metamaterial.