【作者】 徐进；

【导师】 王文祥；

【作者基本信息】 电子科技大学 ， 物理电子学， 2009， 博士

【摘要】 波导设计的目的在于引导能量沿着最小损耗和最小信号失真的轨迹传播。为了提高功率容量可以采用不同方法，包括改变结构形状，采用新型材料等。椭圆结构已经在许多微波器件中得到了广泛的应用，如：滤波器、辐射器、谐振器和宽带传输等。与其他结构相比，椭圆结构仍有许多电磁问题尚待解决。本论文将从结构本身和材料两个方面来研究椭圆结构的电磁特性。鳍线和脊加载波导具有结构紧凑、低截止频率，宽带宽以及低阻抗等特点。对圆和矩形结构加载的研究已经持续了很多年，而对椭圆脊加载的电磁特性的研究则很少，还有待我们去分析解决。椭圆介质柱可作为飞机机身的模型，常被用来研究散射特性。实际结构是具有损耗的，这涉及到对复数马丢函数的研究，对这一问题人们关注较少，通过对复数马丢函数的计算我们对有损耗的椭圆介质问题进行了分析。各向同性非手征材料组成的椭圆结构中，模式可根据其对称性分为偶型模和奇型模。根据马丢函数本身的奇偶性，场具有偶型分量和奇型分量。而在双各向异性和双各向同性媒质中，纵向电、磁场分量将发生耦合，在相应的椭圆结构中将不会有单独的偶型模式和奇型模式。关于这方面的问题本论文进行了详细的讨论。结构型材料的开发，特别是光子晶体材料和复合媒质研究的兴起，使得材料的电磁属性得到了大大的拓展。复合媒质组成的纳米尺度波导有着独特的电磁特性。在论文的第5和第6章，我们讨论了由强各向异性复合媒质构成的椭圆纳米开波导的特殊属性。本论文的组织结构为：第一章为绪论，介绍研究的背景和相关领域的最新动态和存在的问题，阐明论文的研究意义和范围。第二章采用模式匹配法对鳍线加载椭圆波导进行理论推导，得到所有TE、TM模式的完整表达式。采用Rayleigh-Ritz法和多项式表示法，研究了加载圆形脊和矩形脊的椭圆结构，对传输特性与结构尺寸之间的关系进行了讨论。第三章先介绍参数q为复数的马丢函数计算方法，给出计算图形。在此基础上研究圆金属柱涂覆带损耗的椭圆介质的散射问题，对介质损耗和椭圆离心率的影响进行了分析。第四章研究椭圆手征铁氧体的传输特性，根据耦合波方程和边界条件得到特征方程的完整解。给出了场分布图并对其特性进行解释。分析了材料属性和结构参数对色散的影响。第五章分析由各向异性复合媒质组成的椭圆结构电磁特性，根据复合媒质材料参数对波进行分类，推导并讨论了各种情况下的电磁波传输特性。第六章我们采用具有强各向异性的复合材料来构成椭圆纳米开波导，并用仿真软件验证其特性。一些特有属性存在潜在的应用前景，值得得关注。第七章是总结。更多还原

【Abstract】 Waveguides are structures that are typically designed to transmit energy along aspecified trajectory with minimal attenuation and signal distortion.Various avenues canbe pursued when attempting to improve on a waveguides’ capabilities,includingmodifying the shap of structure,or constitutive effective material parameters of theguide.Elliptical waveguides have found wide applications in a variety of microwavecomponents:waveguide filters,radiators,resonators,and wide-band transmission lines,etc.Comparing other shapes,there are still a lot of questions remained in the ellipticalshape structure.It’s nessesary to study the electromagnetics characteristcs with twoapproaches:combining different structures and filling with new materials.Finned and ridged waveguides offer the advantages of low cutoff frequency,widebandwidth,and low impedance.Circular and rectangular ridged waveguide have beenstudies extensively for many years.Elliptical ridged waveguide is still a new domainwhich needs to be explored.The problem of electromagnetic scattering by dielectric elliptical cylindersprovides a useful model to study electromagnetic scattering by the fuselage of aircraft.The scattering by lossy dielectric ellipitic cylinders involves caculating of complexMathieu functions which are ignored by many researchers.The modes in isotropic nonchiral media with elliptical shape are classifiedaccording to their even and odd symmetries with respect to the x axis and/ory axis.Thefield solutions are split into even and odd components in terms of even and odd Mathieufunctions respectively.In bianisotropic and bi-isotropic media,the longitudinalcomponents of electric and magnetic fields are coupled.And no even or odd modesexist individually in such elliptical cylinder.The detailed analysis of ellipticalwaveguide filled by chiroferrite material is presented in this dissertaion.The range of available electromagnetic material properties has been broadened byrecent developments in structured media,notably photonic band gap materials andmetamaterials.Wave propagation in waveguide of nanometer size has unique properties.The unique properties of the elliptical nano-waveguide made from extremelyanisotropic metamaterials have been revealed for in chapter 5 and 6. The structure of this dissertation is presented as follow:Chapter 1 is introduction.The background of research and the obstacles ofpresent research will be firstly explained.Then,the significance and the researchingscope of this dissertation will be presented.In chapter 2,the elliptical waveguide with double infinite thin ridges has beenformulated using mode-matching method.Exact closed-form expressions for eigenvlueproblem of all TE and TM modes are presented.With the Rayleigh-Ritz method andpolynomial representation,the wave propagation characteristics in the ridged ellipticalwaveguide are analyzed.The bandwidth with variation of physical dimensions has beenstudied.In chapter 3,the method for the computation of Mathieu functions with complexparameter q was presented.Electromagnetic scattering by a conducting circular cylindercoated by an elliptic lossy dielectric is derived rigorously by using the mode-matchingtechnique.The effects of dielectric loss and eccentricity on scattering cross section arepresented by numerical techniques.In chapter 4,the propagation characteristics of an elliptical chiroferrite waveguidehave been studied.We have presented correct boundary conditions for ideally conductorwall applicable with coupled wave equations,and obtained the complete solution ofcharacteristics equation.Some field patterns are presented here and have been used toillustrate the complex nature of the fields within the ellipitcal chiral waveguide.Thedispersion characteristics of the ellipitcal chiroferrite waveguide can be freely controlledby varying different medium and structure parameters.In chapter 5,Electromagnetic wave propagation propeties in elliptical cylindermade of metamaterial with permittivity and permeability tensors.The electromagneticwaves are classified according to the parameters of tensors.The formulas for all themodes on the elliptic anisotropic cylinders were derived and discussed.In chapter 6,we propose the realization of elliptical nano-waveguide made ofextremely anisotropic metamaterials,which is confirmed in CST MWS simulations.Theunique properties of this kind of structured material were highlighted.The chapter 7 is conclusion.更多还原