绕于芯棒上的电流环在多层环状媒体中的电磁响应

本文严格导出了绕于任意多层同轴芯棒上的电流环在多层同轴媒质中所产生电磁场的解析解。芯棒和各层媒质中的介电常数、磁导率和电导率均同时考虑在内,所得公式具有普遍意义,场解为含复宗量贝塞尔函数的广义积分。     

电磁场与微波技术

0441,00010867现代电子设备EMC探析/蒋庆全11电子与仪表.一1999,(3),一2一6概述了EMC的研究内容、基本技术、实施方法、数字模型及计算机预测.图3(午)杯形转子永磁电机电磁场的定量分析对电机性能分析、结构设计极为重要.文中将杯形转子展成平面,在直角坐标系内利用分离变量法精确求解转子电磁场,给出了转子内的磁感应强度、电流分布.图2参5(许)0441 00D10868一种杯形转子永磁电机的电磁场分析/赵阳,曹喜滨,邵成勋(哈尔滨工业大学)11黑龙江自动化技术与应用一1999,18(3)一31一330441 00010869绕于芯棒上的电流环在多层环状媒质中的电磁响…     

左手媒质的阻抗边界条件

从Maxwell方程出发，研究了平面波入射到空气和左手媒质的分界面上时，界面附近的电磁场，并将电场和磁场的关系表示为阻抗边界条件表达式，然后与右手媒质的阻抗边界条件进行对比，指出其形式上的统一和计算公式的区别。在此基础上，对多层媒质引用传输线法进行分析，并采用其给出的多层媒质的反射系数计算公式，计算了多层媒质内包含左手媒质时的表面反射系数，并对多层媒质包含左手媒质和右手媒质的情形进行了对比，研究了其反射系数幅度和相位的异同。最后将边界条件应用到阻抗半平面的散射场的计算中，探讨了平面波入射到单面涂敷左手媒质的阻抗半平面上时的散射场，并对场的计算公式作了简单分析。     

多层旋波媒质平板的反射与透射

本文先利用电磁场的边界条件导出平面电磁波垂直入射于多层平板旋波媒质的透射场表达式。然后用传输线理论中的阻抗法,解决了多层平板旋波媒质的反射问题。最后对多层旋波媒质平板的一特例－双层结构型旅波吸波材料进行了计算机辅助设计分析,分析表明,双层代替单层可以在一定程度上改善涂层的吸波特性。     

电磁场、电磁理论、电磁环境

0623113关于由衍射片背面反射光形成的衍射图样的讨论[刊,中]/闫亚奇//广西民族学院学报．—2006,12(2)．—95-96．104(G2) 0623114左手媒质的阻抗边界条件[刊,中]/张鹏飞//雷达科学与技术．—2006,4(3)．—181-184(D)从Maxwell方程出发,研究了平面波入射到空气和左手媒质的分界面上时,界面附近的电磁场,并将电场和磁场的关系表示为阻抗边界条件表达式,然后与右手媒质的阻抗边界条件进行对比,指出其形式上的统一和计算公式的区别。在此基础上,对多层媒质引用传输线法进行分析,并采用其给出的多层媒质的反射系数计算公式,计算了多层媒质内包含左手媒质时的表面反射系数,并对多层媒质包含左手媒质和右手媒质的情形进行丁对比,研究了其反射系数幅度和相位的异同。     

多层双各向同性媒质中电磁波的传输特性

用不对称传输线模型分析了平面电磁波垂直入射于多层双各向同性媒质的反射和透射问题，导出了形式上较简单的计算多层双各向同性媒质界面反射和透射系数公式。为了便于和已有的文献结果相比较，给出计算实例，结果表明，用此公式得出的结果和文献结果一致，为计算多层双各向同性媒质的反射和透射带来方便；同时，对双各向同性媒质，非互易参数和手征参数的改变对反射和透射系数都有较大的影响。     

垂直电偶极子在负折射媒质涂覆基底上产生的场

研究了垂直电偶极子在负折射媒质涂覆的理想导电基底上产生的电磁场,获得了场分量的解析表达式.分析和计算结果表明,电偶极子激发的电磁场可分解为直达波、反射波、侧面波和表面波.其中表面波在负折射媒质表面传播的波数介于空气层和介质层中传播波数之间,其幅度在距离向按波的几何扩散规律衰减,在垂直于介质层方向则以正弦或余弦规律变化.由于存在三种传播波数的波,它们共同作用形成的总场将发生复杂的干涉现象.     

电磁学中媒质介电性的分析与探讨

众所周知,电磁场与电磁波理论的深入理解是非专业人员难于做到的。而对于媒质的介电性和电导性关系,现有专业书籍更是涉猎甚微。根据这一实际情况,本文有针对性地展开了分析和探讨。本文首先分析了静态场和动态场媒质的介电性,然后对静态场和动态场中媒质的介电常数和电导率进行了分析和探讨,最后分析了良导电媒质(金属)的介电常数。希望本文能够有助于电子工程师对相关问题的深入理解,并提供有价值的参考。     

多层环状导电媒质中离轴偶极子辐射场的级数解

当偶极子源(电偶极子或磁偶极子)置于多层环状导电媒质中偏离轴线的任意一点时,所激发的电磁场既存在TE波又存在TM波。文中导出了各层媒质中电磁场的通解,用边界条件建立了系数传递矩阵,从而完全确定了电磁场表达式。计算实例中给出了一组离轴偶极子的响应曲线。     

非对称电偶极在地层中的热效应解析解

用近似法分析了有耗媒质中非对称电偶极的激励场,得到一个场和焦耳热的简单的解析表达式。与传统的对称型半波振子公式相比较,其下端导体的电流分布表达式相同,当下端导体为四分之一波长时激励近场表达式相近。结合典型储油层给出一些计算结果,对电磁波采油技术有参考价值。     

On the excitation of a circular loop antenna by travelling-and standing-wave current distributions

Presented here is an exact formulation of the electric and magnetic (EM) fields radiated by a circular loop antenna, assuming both travelling- and standing-wave current distributions. By using a differential current element positioned in an azimuthal direction as the starting point, the paper systematically develops the EM fields radiated by the circular loop via a vector potential theory. This approach leads to a general integral representation for the radiation characteristics of the loop antenna where we completely evaluate the resulting expressions, when the excitations of the loop assume travelling- and standing-wave distribution forms. In addition, this paper briefly examines a method to generate approximately such current distributions by coupling the loop to a two- or four-wire transmission line. Furthermore, the paper discusses a graphical representation of the current distribution plotted as a function of frequency or loop size. From the field expressions determined, we derive generalized closed-form results for some important design parameters for the loop antenna. These parameters include the radial component of the Poynting vector, the total power radiated by the loop, the directivity, the radiation resistance, and the effective area and height of the antenna. When we specialize to the important case of uniform current excitation, the exact values of the parameters deduced from the general expressions, are summarized and exhibited in a comprehensive table. This table facilitates the computations of these important physical parameters. Further analysis involving small argument and asymptotic approximations in the residts for the travelling-wave current excitation leads to closed-form expressions in terms of tabulated functions. Numerical results presented, include the fields radiated by the loop when the standing-wave current excitation admits a Fourier series representation. The present approach via potential theory reveals that the fields can be calculated in any arbitrary direction : this is consistent with a previous observation of Knudsen (1951, 1953) who employed a different approach.     

三层导电媒质中环天线的远区电磁场

快速准确地计算分层导电媒质中的环天线产生的电磁场一直受到人们的重视。由于这个问题常常涉及到Ｓｏｍｍｅｒｆｅｌｄ型积分的计算问题，因而是相当困难的。本文采用一种计算远场Ｓｏｍｍｅｒｆｅｌｄ型积分的新方法，结合复镜象理论，快速方便地得出了三层导电媒质中环天线远区场强的解析表达式。该方法可以很方便地推广应用到类似情况的远区场强的计算中去。     

研究双稳半导体激光器的新方法──逐点跟踪法＊

逐点计算非均匀泵浦半导体激光器输出双稳环上四个关键点处的运行参量,对吸收型双稳半导体激光器进行了研究。该法不但可以给出双稳激光器“启动”和“下跳“点的阈值电流和相应的输出功率,而且还可以给出用这些值来表示的增益截面的解析表达式,这将使得实验上可以简单地由测量到的双稳环的宽度和高度来确定难于测定的增益截面。     

Air to undersea communication with magnetic dipoles

Simplified expressions are derived for the electromagnetic fields produced by a vertical or horizontal magnetic dipole (loop antenna) located in air above the sea. The expressions hold over the quasi-near range in both media subject to certain mild restrictions. The solutions are obtained by first applying the boundary conditions to determine the magnetic Hertz potentialbar{pi}^{ast}in the form of Sommerfeld integrals, and then relating these to two auxiliary integralsU, Vand their derivatives, asymptotic series for which are obtained by extending the work of Baños and Wesley. The horizontal magnetic dipole (loop in the vertical plane) is found to be superior to the vertically-oriented dipole of the same size and excitation from the point of view of field strength induced in the sea at large distances from the source. A comparison with previously published results for the electric dipole shows the magnetic dipole to be better, provided the number of turns in the loop exceeds a certain minimum. An approximate analysis on the basis of equal powers also shows the magnetic dipole to be better except for points near the outer rim of the quasi-near range, where the two types of dipoles are equivalent.     

海水中极低频水平电偶极子电磁场的解析解

将海水看作线性、均匀、各向同性的半无限大导体空间,利用汉克尔变换及开尔文函数的近似展开式,推导求得了极低频时谐水平电偶极子在海水中产生的电磁场的近似解析表达式.运用推导的解析表达式,可以计算海水中任意场点的电磁场值.     

垂直电偶极子在涂敷介质导电平面上激起的场Ⅱ

对垂直电偶极子（VED）在涂敷介质层的非理想导电基底上激起的电磁场进行了讨论,获得了便于计算的解析表达式,并进行了数值计算。     

A reciprocity theorem for electromagnetic fields with general time dependence

A reciprocity theorem for electromagnetic fields with general time dependence has been derived in the time domain, and thus the result is applicable to fields whose time dependences are not Fourier transformable functions. The region to which the theorem applies may consist of dissipative, dispersive, nonhomogeneous, and anisotropic (but nongyrotropic) media, and all these properties may extend to infinity. Based on this theorem a variational expression which provides an approximation for calculating scattered fields has been obtained. The meaning of the approximation for the fields as arbitrary functions of time is discussed, together with three types of practical detecting systems, namely, square law, full-wave bridge, and single diode. For the latter two types, it is found that the variational expression yields an upper bound to the signal at the output of the detector.     

Slant Dielectric Interface Discontinuity in a Waveguide (Short Papers)

The reflection and transmission of electromagnetic waves by a slant interface between two dielectric media is investigated. By using suitable Green's functions and a geometrical optics approximation for the field on the dielectric interface, expressions for the transmitted and reflected fields are derived. The approximate results obtained in this manner are compared with the available numerical data and are shown to be fairly accurate for a number of cases of interest.     

理想导体金属谐振腔电磁场微扰理论研究

根据电磁场Helmholtz方程与定态薛定谔方程的相似性，给出了金属谐振腔电磁场的微扰理论：在金属腔中放入一介质体时，原来空腔中电磁场的分布和谐振频率会发生改变。发生改变后的电磁场可以用原来所有模式电磁场展开。若引入的介质体很小或相对介电常数和磁导率接近于1，就可把它看成微扰。导出了谐振频率和电磁场分布的一级、二级近似解析表达式。指出了此理沦的适用范围，并对结果进行了讨论。