各向同性等离子体覆盖金属天线辐射增强现象  

Radiation enhancement phenomenon of isotropic plasma layer coated cylinderical metal antenna

作　　者：李文秋 唐彦娜 刘雅琳 马维聪 王刚 Li Wen-Qiu;Tang Yan-Na;Liu Ya-Lin;Ma Wei-Cong;Wang Gang(Aerospace Information Research Institute,Chinese Academy of Sciences,Beijing 100190,China;Xi’an Institute of Applied Optics,Xi’an 710065,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国科学院空天信息创新研究院,北京100190 [2]西安应用光学研究所,西安710065 [3]中国科学院大学,北京100049

出　　处：《物理学报》2023年第13期126-133,共8页Acta Physica Sinica

基　　金：中国科学院空天信息创新研究院高功率微波源与技术重点实验室(批准号:Y9D0260H93)资助的课题。

摘　　要：以飞行器再入大气层时面临的通信“黑障”问题为研究背景,考虑粒子动力学效应,采用温等离子体介电常数模型,理论分析了各向同性等离子体覆盖圆柱金属天线构型中角向对称电磁模式的色散特性、传播特性及辐射特性.研究结果表明:在低气压、电磁波频率w/(2π)=1 GHz参量条件下,界于金属天线表面和主等离子体层之间的鞘层厚度约为几个德拜长度;角向对称模在天线表面的传播属于快波(波的相速大于光速)辐射,且存在一个临界等离子体密度,超过此临界值电磁波变为消逝波;存在一个临界归一化鞘层厚度(ι/λ_(De))_(pha)(或(ι/λ_(De))_(att)),超过此临界值时,相位常数(或衰减常数)幅值开始陡升(或陡降),即波的传播特性发生显著改变;当金属天线半径为3倍等离子体趋肤深度、鞘层厚度为整个等离子体层厚度的0.1倍时,电场和功率出现“椭圆形轮廓”辐射增强现象,其可能是由等离子体频率共振和等离子体-鞘层-天线系统阻抗共振引起,这些结论为相控阵天线的高分辨率成像等问题提供了理论思路.The blackout problem suffered by hypersonic vehicles as they re-enter the atmosphere is essential for effective communication of hypersonic vehicles.Aiming to solve this problem,in this paper,we proposed an antenna–sheath–plasma layer configuration,in which a thin plasma layer covered cylindrical metal antenna model is employed to investigate the radiation enhancement phenomenon by solving the dispersion equation of electromagnetic mode under optimized parameter conditions.Analytical results show that when the neutral gas pressure is low(p=0.5 mTorr)and the antenna radius is triple the plasma skin depth,the thickness of the sheath between the surface of metal cylindrical antenna and plasma layer is about several Debye lengths,the azimuthally symmetric wave(m=0 mode)that propagates along the antenna surface belongs to the fast wave(the phase velocity is greater than the light speed),there exists a critical plasma frequency wpe(or plasma density n0),above which the propagating mode becomes evanescent wave;for the propagation characteristic,there exists a critical normalized sheath thickness(ι/λ_(De))_(pha)(or(ι/λ_(De))_(att)),above which the phase constant(or the attenuation constant)begins to increase(or decrease)sharply,which indicates a significant change in the propagation property of the propagating mode;most importantly,when the wave frequency w/2π=1 GHz,sheath thickness is one tenth of the whole plasma layer thickness,owing to the electron plasma frequency resonance and antenna-sheath-plasma resonance effect,the maximum radiation intensity of the symmetric wave exhibits an elliptical-like profile near w_(pe)/w=1 and w_(pe)/w≈1.33,respectively,while only a single-point radiation enhancement occurs at frequencies far from GHz range.These conclusions not only provide a method to solve or alleviate the blackout problem of GHz frequency communication faced by the hypersonic vehicles when they re-enter the atmosphere,but also have potential applications in high-resolution imaging induced by plasmonic mi

关 键 词：等离子体 鞘层 电磁波辐射 色散关系 

分 类 号：TN820[电子电信—信息与通信工程] O53[理学—等离子体物理]