应用于动态核极化核磁共振系统的改进型传输线研究（英文）

基于几何光学理论和矢量衍射理论,设计了263 GHz DNP-NMR谱仪的改进反射镜系统,并进行了数值模拟.该系统包括两个波纹波导、一个抛物面镜和一个角度可调的相位校正镜.仿真结果表明,获得了聚焦良好的类高斯输出光束,其标量高斯模含量为99.90%,矢量高斯模含量为99.55%.只有通过调整相位校正镜的角度来匹配DNP-NMR样品,才能改变输出光束的方向.当输出光束方向在±15°变化时,标量高斯模含量约为99.57%,矢量高斯模含量约为98.97%.     

应用于动态核极化核磁共振系统的改进型传输线研究

基于几何光学理论和矢量衍射理论,设计了263 GHz DNP-NMR谱仪的改进反射镜系统,并进行了数值模拟.该系统包括两个波纹波导、一个抛物面镜和一个角度可调的相位校正镜.仿真结果表明,获得了聚焦良好的类高斯输出光束,其标量高斯模含量为99.90%,矢量高斯模含量为99.55%.只有通过调整相位校正镜的角度来匹配DNP-NMR样品,才能改变输出光束的方向.当输出光束方向在±15^o变化时,标量高斯模含量约为99.57%,矢量高斯模含量约为98.97%.     

求解电磁场并矢格林函数的新方法

本文提出了求解电磁场边值问题的新方法:把矢量波方程的边值问题化为对应的标量波方程的边值问题加上两个附加的矢量微分运算的问题。用这种方法可以很方便地求解所有现在用并矢格林函数的本征展开法所能求得的各种并矢格林函数。可以求解用现有的方法很难求解的比较复杂系统的并矢格林函数。文中给出了加载的谐振腔的并矢格林函数就是其中的一例。     

电磁场在矢量波函数空间的完全射影定理

证明了广义的亥姆赫兹定理－电磁场在矢量波函数的完全射影定理。在这一定理中每一个任意的电磁矢量函数都可以在矢量波函数空间中被唯一地分离成三个独立的分量,每一个分量都可以用一个标量函数来表示。     

矢量波函数空间的电磁矢量恰当射影

提出了一种简化电磁场问题求解的新方法，将电磁场矢量的无旋场部分和无散场部分各自应用一个满足二阶方程的标量函数表示出来，然后由此分析了电磁场矢量在矢量波函数空间的恰当射影问题，并给出用一个标量格林函数构造的无散电磁场并矢格林函数。     

用电磁场算子理论求波导复合系统的本征值

该文用并矢格林函数方法通过虚拟边界的电场和磁场的耦合求解波导复合结构的本征值,所采用的并矢格林函数没有奇异项,可以用标量格林函数来表示并进行计算,因此不仅可以计算横电与横磁模的基模和高次模式,还可以计算存在两个孪生模式的复合系统。该文同时还对经典场论中常用的一些定理,如面旋度定理进行了探讨。     

推广的赫姆霍兹定理及其在电磁理论中的应用

本文证明了在直角、画柱和球坐标系的规则边界的系统内,一个任意的矢量一定可以分解为无旋场、横电模场和横磁模场三个相互正交的分量,每一个分量都可用一个标量函数来描述。并在此基础上证明了这些系统内的{L、M和N}矢量波函数系的完备性。由此说明了一个矢量函数空间不仅可以通过它在欧氏空间中的射影分解为三个不相交的子空间,同样可以通过它在矢量波函数系上的射影分解为三个不相交的子空间。     

L波段波导高方向性取样装置

微波矢量网络分析仪,标量网络分析仪和扫频测试仪,在构成高性能波导宽带扫频测量系统时,都需要波导宽带高方面性取样装置。在厘米波到毫米波的高频波段,它是由波导宽带高方向性耦合器来实现的。在分米波段,由于波长长,≤≤波导尺寸大,波导宽带高方向性耦合器的长度可长到数米,实际使用极不方便,一种基于宽带波导魔T电桥L波段的波导微波测量高方向性取样装置在西安恒达微波技术开发公司研制成功,从而解决了大尺寸波导宽带高性能测量的问题。     

对象间矢量感应聚类算法

从万有引力角度考虑,质点之间相互影响包括距离和方向两个方面.本文讨论数据之间的矢量感应,并将其应用于聚类算法ⅥCA.引入对象的标量感应函数和方向感应函数,提出矢量感应函数概念.并给出确定方向感应函数的两个方法:方向相似度法和累加法.将核心对象邻域中的对象投影,进行向量单位化,考察核心对象的邻域均匀感应程度,将与均匀感应...     

一般光波导标量分析的一种通用方法

多种传统分析方法的系统比较表明，按照无限区域内完备正交函数系展开，采用优化收敛系数和简单修正方法的Ｇａｌｅｒｋｉｎ方法，是一种分析光波导的通用方法，阶跃型剖面弱导矩形光波导的标量分析结果，证实了该方法精度高，收敛快，可避免多种传统方法的诸多弊端。     

An implementation of the vectorial finite element analysis ofanisotropic waveguides through a general-purpose PDE software

This paper reports on the major progress in the development of an intelligent, interactive and automated system, based on the vector finite element method, and implemented within PDE/Protran problem solving environment. The system is known as WAVEGIDE and was originally developed by the authors for an efficient solution of inhomogeneous dielectric waveguides. In this paper, it has been further extended to the solution of anisotropic waveguiding structures. With our system, through an interactive “question-and-answer” session, which requires minimal knowledge of programming, the problem can be defined using high level PDE/Protran commands. It can then be simply and quickly solved by the main processor within this intelligent environment. To verify the convergence and accuracy of the present approach, numerical results (with respect to the grid density and element order) for a rectangular metallic waveguide half filled with dielectric are given and compared with other finite element methods. Numerical results for an anisotropic dielectric rectangular waveguide are also presented. These results clearly illustrate the accuracy and the ease of use of the modified WAVEGIDE program     

Two-dimensional rectangular lattice distributed feedback lasers: Acoupled-mode analysis of TE guided modes

Two-dimensional rectangular lattice distributed feedback lasers in a waveguide geometry are described by a coupled-mode analysis of a scalar wave equation derived from a vector field for TE guided modes. A detailed analysis is provided for a two-dimensional grating which allows the method of separation of variables for the scalar wave equation so that the threshold conditions are described by those of two orthogonal one-dimensional gratings. We present the correct definitions of threshold gain and detuning of the two-dimensional distributed feedback laser, and also the optimum design conditions for the minimization of the threshold gain. It is found that there is an optimum structural angle for the given area and periods of the two-dimensional grating     

Finite Element Analysis Waveguides of Optical

A finite element program for the analysis of anisotropic optical waveguides is described. The appearance of spurious numerical modes, due to the fact that the functional is nonpositive definite is discussed and a possible solution to the problem is presented. For isotropic waveguides it is shown that both EH- and HE-type modes can be very accurately approximated by two different scalar finite element programs. Finally, a method for calculating the attenuation of leaky modes in a single material integrated optic waveguide using this scalar finite element method is proposed.     

Efficient solution of the differential form of Maxwell's equationsin rectangular regions

One of the problems of the finite element and the finite difference method is that as the dimension of the problem increases, the condition number of the system matrix increases as Θ(1/h² ) (of the order of h², where h is the subsection length). Through the use of a suitable basis function tailored for rectangular regions, it is shown that the growth of the condition number can be checked while still retaining the sparsity of the system matrix. This is achieved through a proper choice of entire domain basis functions. Numerical examples have been presented for efficient solution of waveguide problems with rectangular regions utilizing this approach     

基于半解析谱元法的各向异性介质PBG结构传输特性的研究

将精细积分方法与谱单元法结合,对含有各向异性介质的波导介质层光子带隙(PBG)结构的传输特性进行了研究.从矢量波动方程相对应的单变量变分形式出发,对含有各向异性介质波导横截面采用谱单元进行离散,引入对偶变量,将单变量变分原理导入到哈密顿体系,利用精细积分法求出出口刚度矩阵.数值算例将半解析谱元法与常规有限元法、半解析有限元法进行了比较,表明本文方法具有高精度、高效率的特点,而且计算精度随着谱单元阶数的增加呈指数增长.     

A full-wave analysis of an arbitrarily shaped dielectric waveguideusing Green's scalar identity

An integral equation analysis is proposed to determine the phase constant of an arbitrarily shaped dielectric waveguide. The main feature of this approach is the use of Green's scalar identity in which only simple contour integrals have to be evaluated. Different scalar Green's functions are considered to satisfy the boundary conditions for the electric and magnetic fields in each region. This approach is combined with the boundary element technique with linear elements for the computation. The case of the rectangular dielectric image waveguide is discussed. and numerical results are shown to be consistent with other theories and experiments. The cases of hollow rectangular and semicircular image waveguides are analyzed, and numerical results are presented     

Optical waveguide dispersion characteristics from the scalar wave equation

The electric and magnetic fields of an optical waveguide are well represented as derivatives of a linearly polarized vector potential. This vector potential obeys a scalar wave equation. Through the use of a variational principle one may obtain good approximations to the dispersion relation, however, without resolution of the birefringence. A simple perturbational approach yields the birefringence. Universal plots may be obtained in this way for TE and TM modes for rectangular channel waveguides with small index discontinuities.     

矩形槽波导的模式图

本文用有限元法分析了矩形槽波导。对矩形波导的计算验证了我们的有限元程序是有效的。文中给出的矩形槽波导模式图有助于设计基于矩形槽波导的短毫米波和亚毫米波器件。     

Absorbing boundary conditions for the finite-element analysis ofplanar devices

The finite-element method is used to determine the scattering matrices of open devices in two dimensions. Microwave and optical devices in which the fields are not confined to a finite region can be analyzed with the finite-element method if special boundary conditions are used to absorb outgoing radiation. The absorbing boundary conditions can be imposed by the addition of two terms to the usual functional for the scalar Helmholtz equation. Universal matrices are introduced to allow the additional terms to be easily assembled, for polynomial orders one through four. Results are given for the impedance of a parallel-plate waveguide radiating into free space and for the scattering parameters of three dielectric slab waveguide devices: a rectangular discontinuity, a feed structure, and a junction