【作者】 张忠祥；

【导师】 徐善驾；

【作者基本信息】 中国科学技术大学 ， 电磁场与微波技术， 2007， 博士

【摘要】 最近几年来，一种被称为“左手材料”(left-handed materials，LHMs)的人工等效材料在国际固体物理、材料科学、光学和应用电磁学领域内开始获得愈来愈广泛的青睐，对其的研究正呈现迅速发展之势，而它的出现却是源于上世纪60年代前苏联科学家V. G. Vesalago的假想。物理学中，介电常数ε和磁导率μ是描述材料媒质中电磁场性质的最基本的两个物理量。在已知的物质世界中，对于电磁媒质而言，介电常数ε和磁导率μ都是正值，电场、磁场和波矢量三者构成右手关系，这样的物质被称为右手材料(right-handed materials，RHMs)，这种右手规则一直以来被认为是物质世界的常规，但这一常规却在上世纪60年代开始遭遇颠覆性的挑战。在1967年，前苏联物理学家V. G. Vesalago在前苏联一个学术刊物上发表了一篇论文，首次报道了他在理论研究中对物质电磁学性质的新发现，即：当ε和μ都为负值时，电场、磁场和波矢量之间构成左手关系。他称这种假想的物质为左手材料，同时指出，电磁波在左手材料中的行为与在右手材料中相反，比如逆多普勒效应(Reversed Doppler Effect)、逆斯涅尔折射效应(Reversed Snell Refraction)及逆Cerenkov辐射效应(Reversed Cerenkov Radiation)等等。这篇论文引起了一位英国人的关注，1968年被译成英文重新发表在另一个前苏联物理类学术刊物上。但几乎无人意识到，材料世界从此翻开新的一页。由于自然界中并没有左手材料的存在，左手材料的研究发展并不是一帆风顺的，尽管它有很多奇异的性质，但都只是停留在理论上，所以这一怪诞的假设并没有被人们所接受，直到上世纪末才开始出现一丝曙光：1996年，英国皇家学院John Pendry等人指出可以用细金属导线阵列构造介电常数ε为负的人工媒质，1999年又指出可以用金属开口谐振环阵列构造磁导率μ为负的人工媒质。2001年，美国加州大学圣地亚哥分校的David Smith等人在Science杂志上发表文章，沿用Pendry的方法，构造出了介电常数与磁导率同时为负的人工媒质，并通过实验观察到了微波频段的电磁波通过这种人工媒质与空气的交界面时发生的“负折射”现象。从此这类人工媒质的研究成为国际电磁学界一个引人注目的前沿领域，并引发了热烈的讨论。2002年底，美国麻省理工学院孔金瓯教授从理论上证明了左手材料存在的合理性，并称这种人工介质可用来制造高指向性的天线、聚焦微波波束、实现“完美透镜”、用于电磁波隐身等等。左手材料的前景开始引发学术界、产业界尤其是军方的无限遐想。2003年是左手材料研究获得多项突破的一年。美国西雅图Boeing PhantomWorks的C. Parazzoli与加拿大University of Toronto电机系的G. V. Eleftheriades所领导的两组研究人员在实验中直接观测到了负折射定律：Iowa State University的S. Foteinopoulou也发表了利用光子晶体做为介质的左手物质理论仿真结果；美国麻省理工学院的E. Cubukcu和K. Aydin在《自然》杂志发表文章，描述了电磁波在两维光子晶体中的负折射现象的实验结果。基于科学家们的多项发现，左手材料的研制赫然进入了美国《科学》杂志评出的2003年度全球十大科学进展，引起全球瞩目。由于前面利用金属细导线和开口谐振环阵列等效实现的左手材料，具有损耗大和左手频段窄等特点，很难在微波和毫米波系统中获得应用。2003年开始，美国Arthur A. Oliner、T. Itoh和加拿大George V. Eleftheriades教授利用对偶传输线模型等效实现了一维和两维结构的左手导波结构，证明了具有低损耗和宽频带的特性，为左手材料在微波和毫米波系统中的应用提供了可能，并给出了一些在微波领域中的应用，表现出一些左手材料独有的特性。同时，左手材料的显著特点是它的介电常数和磁导率都是负数，所以人们也称之为“双负介质(材料)(Double Negative Material, DNM)”，通常也被称为“负折射系数材料(Material with Negative Refractive Index, MNR)”，或简称“负材料”。本论文主要围绕着左手材料的人工等效实现和在微波及毫米波系统中的应用问题，在基于左手传输线电路模型的基础上，提出了新型左手传输线单元结构，该单元结构具有着结构简单紧凑、损耗低和左手频带宽等优点。同时，系统的分析了该结构单元的电路模型和色散关系，并给出了左手传输线在微波和毫米波系统中的创新性应用。论文首先简要介绍了左手材料概念的提出和当今国际电磁学界对左手材料的研究进程。然后，在基于左手传输线电路模型的基础上，提出了新型的左手传输线微带单元结构，该单元结构具有结构紧凑、体积小和宽频带、低损耗的特点，同时给出了该单元结构的电路模型参数的提取过程，为在微波和毫米波系统中的应用提供了基础，并在最后实验验证了左手微带传输线的等效实现。随后，论文对一维左手微带传输线在微波和毫米波系统中的应用进行了深入的研究分析。由于左手材料和传统的右手材料相比较，具有如下独有的特性：后向辐射和相位超前的特性，同时在利用传统的右手材料来等效实现左手材料的过程中，由于不可避免的引入了右手寄生参量的存在，所以等效实现的左手材料不是一个纯的左手材料，而是一个左手材料和右手材料的混合结构，等等，这些特性决定着人工等效左手材料在电磁领域有着一些创新性的应用。首先，由于人工等效的左手传输线是一个左—右手混合传输线，当处于平衡状态的时候，是一个左手的高通网络和右手的低通网络混合结构，通过合适的选择参数可以得到一个超宽带的滤波网络，即构成超宽带滤波器；其次，利用左手传输线的相位超前特性，可以很容易的应用到对相位需要超前的单元中去，本论文给出了由左手微带传输线构成的新型平衡—不平衡转换器，该转换器具有结构简单，设计方便等优点；最后，同样是利用相位超前特性，提出了一种新型微波和毫米波系统天线阵列的馈电网络，可以根据设计需要来调整天线阵列单元间的相位差，从而来控制天线阵列辐射方向图的偏转，同时该馈电网络具有结构简单，损耗小等优点。同时，论文也给出了单层两维左手传输线微带等效实现单元结构，该单元结构具有结构简单、尺寸紧凑、便于加工和低损耗、宽频带等优点，同时也给出了该单元结构的电路模型参数的提取过程，为在微波和毫米波系统中左手材料的平面结构的应用提供了基础。最后，论文同时对两维左手微带传输线在微波和毫米波系统中的应用也进行了深入的研究分析。由于电磁波在左手材料和右手材料的分界面处具有逆斯涅尔折射效应，和左手材料对消失波的放大作用，早在1968年，前苏联科学家V．G．Vesalago就提出了可以利用左手材料来实现完美透镜的假设。本论文给出了，由提出的新型两维左手微带单元结构组成的左手材料和两边端接右手平板波导构成的完美透镜模型，该模型证明了左手材料的逆斯涅尔折射效应和消失波的放大作用。本论文在基于左手传输线电路模型的基础上，提出了新型一维和两维左手传输线的微带单元结构，并基于提出的单元结构给出了它们在微波和毫米波系统中的一些创新性的应用，同时论文中提出的一些设计方法对左手材料和微波及毫米波系统的设计也有着重要的参考价值。更多还原

【Abstract】 In recent years, a kind of "left-handed materials"(LHMs), the artificial equivalent materials in solid-state physics, materials science, optical and electromagnetic fields starts to obtain the increasingly widespread favor, and the research is showing its rapid development. But its appearance was acturally from the former Soviet Union scientists V. G. Vesalago imagination in the 1960s.In physics, the permittivityεand the permeabilityμare the two fundamental physical quantities, which describe the electromagnetism nature of the material. In the known material world, to the electromagnetic medium, the permittivityεand the permeabilityμare both positive, where the electric field, the magnetic filed and the wave vector satisfy the right hand relations, and such materials are called right-handed materials (RHMs). Since this kind of right-hand rule was considered necessarily the natural convention, but this convention had been suffering the subversive challenge from the 1960s. In 1967, the former Soviet Union physicist V. G. Vesalago published a paper in a former Soviet Union academic publication, and had reported for the first time in novel discovery relating to the fundamental research of the material electromagnetic nature. Namely, the electric field, the magnetic filed and the wave vector satisfy the left hand relations when the permittivityεand the permeabilityμare simultaneity negative. He called this kind of imaginary material the left-handed material (LHM), and predicted that the electromagnetic behavior in LHM was opposite to that in the RHM. For instances, the reversed Doppler Effect, the reversed Snell Refraction and the reversed Cerenkov Radiation, etc. This paper aroused an English man’s interest, and was translated into English for publishing in another former Soviet Union physics academic publication in 1968. However, hardly anybody at that time realized that the material world henceforth opens the new page.Because there is no left-handed materials existence in the nature world, the research on the LHMs is not plain sailing. Although it has so many strange natures, all the research is limited to theoretical analysis. The supposition had not been accepted by the people until the end of the last century, when the first light of morning appeared. In 1996, John Pendry and his group in the Blackett Lab. of United Kingdom pointed out that the negative permittivityεmedium can be constructed from the thin copper wires structure. And in 1999, they demonstrated that the negative permeabilityμmedium can be constructed from the structure of split-ring resonators.In 2001, David Smith and his group at University of California, San Diego, published the paper on the Science magazine, in which the artificial material with the permittivityεand the permeabilityμsimultaneity negative was constructed by John Pendry.By the end of 2002, Professor Jin Au Kong from MIT proved the rationality of the existence of LHM, and pointed out that this kind of artificial material are highly promising in high- directional antennas making, microwave beam focused to achieve "perfect lens", the electromagnetic stealth and so on. The prospect of LHM starts to arouse the infinite dreams of the academia, the industrial field and particular the military.2003 was the golden year for LHM researching in which many breakthroughs were obtained. The group at Boeing Phantom Works and another group at University of Toronto demonstrated the concept of a negative refraction in the labs. And S. Foteinopoulo at Iowa State University also published the simulated results of the LHMs that constructed with photonic crystal. Based on these discoveries, the development of LHMs impressively entered the world’s top ten scientific advances selected by the Science Magazine in 2003, and attracted global attention.Because the LHMs are composed of the thin copper wires and split-ring resonators, which have large insert-loss and narrow left-handed frequency band, and so on, it is very difficultly to be applied in microwave and millimeter wave system. In the begin of 2003, Professor Arthur A. Olinear, T. Itol and George V. Eleftheriades realized that a transmission line approach towards LHMs was possible, which had been demonstrated by having low loss and wide left-haned frequency band, and provided the possibility for LHMs in the microwave and millimeter wave system applications.With the remarkable characteristic of LHMs of simultaneously negative permittivityε and permeabilityμ, the LHM is also called Double Negative Material (DNM), or Material with Negative Refractive Index (MNR).The concept of LHM and the study course in the international electromagnetism are briefly introduced at the beginning of the thesis. Then, based on the model of left-handed transmission lines (LH-TLs), a novel left-handed microstrip unit structure is presented, which has smaller size and lower insert-loss. At the same time, the extraction process of the model parameters in the unit structure is given, which provides the foundation in microwave and millimeter wave system applications. The experiment confirmes the equivalent realization of LH-TLsThen, the 1-dimension LH-TLs applications researches in microwave and millimeter wave system are analyzed. At first, the TLs approach of LH materials is based on the dual of the conventional transmission lines. Because of unavoidable parasitic series inductance and shunt capacitance resulting in a RH contribution increasing with frequency, the LH transmission line is a composite right-left handed transmission line (CRLH-TL). We obtain an ultra-wide band (UWB) filter network through the appropriate choice parameters. Second, based on the advance phase shift characteristics of LHMs, a novel balun structure with CRLH-TL is presented. Combined the traditional right-handed line with CRLH-TL, the process of design balun will become more easy and simple. At last, a novel feeding network for 2-dimension millimeter wave microstrip patch arrays with CRLH-TL is proposed. Because of the simpler structure and the shorter length of the CRLH-TL feeding network, the antenna array is of higher gain than that with the conventional parallel feed network. Besides, the radiation pattern shift resulting from the traditional parallel-series feeding network is removed since no inserting phases shift are introduced in the patch elements using the novel feeding structure.Synchronously, a novel unit of planar distributed structure with double negative material (DNM) is proposed. The present unit cell implemented with microstrip structure has composite structure on single-layer but not two layers as did before. By using interdigital capacitor instead of the former mushroom structure with caps, the structure has depressed the left-handed transmission frequency band than the former one. And the extraction process of the model parameters in the unit structure is also given. Also, a new DNM lens based on the present planar distributed 2-D structure, which id interfaced with two parallel-plate waveguides (PPWs) is designed and simulated. The focusing/refocusing effect is observed by full-wave simulations.The investigation in this thesis is of theoretically and practically significant for realization the microstrip unit structure of the LH-TLs, and for novel applications in the microwave and millimeter wave system. Furthermore, this work is valuable for design of components in the microstrip circuits and microwave system based on the left-handed materials.更多还原