Analysis of radiation characteristics of a finite-lengthtransmission line using a circuit-concept approach

The radiation phenomenon from a transmission line of finite length is described. Based on the hypothesis of reciprocity between the coupling of an external wave to a transmission line and the radiation from a transmission line, a set of models for both phenomena is implemented using a six-terminal network. The goal is to find out what current is induced in each terminal load of the network. The radiation characteristics of finite-length lines such as radiation fields, radiation power-density, and radiation coefficients are considered. Experiments using both straight lines and bent lines have been performed to validate the theory     

A study on the radiation loss from a bent transmission line

This paper deals with the radiation loss of bent transmission lines in order to determine the most optimal design for a bent line from the standpoint of radiation loss. We have used the method of moments (MoM) for a numerical analysis on the radiation for different structures of bent lines and we have found that the simplest right-angle bend is the best with the least radiation loss. This theoretical expectation was confirmed experimentally     

Analysis of coaxial waveguide partially filled with chiral media

In this paper, the canonical problem of coaxial waveguide partially filled with chiral media is analyzed by a new equivalent transmission line network method. Both radial transmission lines in the cross section and multi-mode transmission lines in the longitudinal direction are introduced. The symmetrical properties of the structure are also discussed. Therefore, this method brings a clear physical picture into the wave propagation phenomena. Based on the analysis, the notable features and the role of the chirality parameter of the medium on the reflected and transmitted guided waves are discussed.     

A new radial transmission line network approach for symmetrical modes in circular chirowaveguides

In this paper, the dispersion characteristics of symmetrical modes in circular chirowaveguides are analyzed by a new equivalent transmission line network method. Radial transmission lines in the transverse cross section are introduced. In the transmission line network, the right-circularly polarized (RCP) wave and the left-circularly polarized (LCP) wave can propagate independently in the uniform regions and couple only at the interface. Therefore, this method brings a clear physical picture into the wave propagation phenomena. Based on the analysis, two interesting effects due to mode coupling and leakage are carefully studied.     

Electromagnetic modes in conical transmission lines withapplication to the linearly tapered slot antenna

A transmission line analysis of the bow-tie antenna and the linearly tapered slot antenna (LTSA) is presented. These structures belong to the class of conical transmission lines defined here in terms of conical coordinates. A complete set of solutions of the Helmholtz equation is obtained exhibiting TE and TM modes. Modal fields are expressed by Lame (1837) and Bessel-Schelkunoff functions. TE and TM eigenmode analysis is particularized to the bow-tie structure. Bow-tie antenna and LTSA are shown to be dual conical transmission lines by the image method and Babinet's principle. The modes of LTSA are calculated on the basis of the results obtained for the bow-tie structure. The radiation pattern of the LTSA is computed as the integral of a closed-form expression of the dyadic Green's function weighted by the modal electric field distribution over the slot aperture. The obtained dominant mode radiation patterns are validated by measurements from the literature. The radiation patterns of the first two-order modes are calculated and compared     

A Compact Slot Antenna Utilizing a Right/Left-Handed Transmission Line Feed

A novel compact planar antenna utilizing cascaded right/left-handed transmission lines is proposed. The significance of layout planning with respect to radiation is investigated and discussed in this paper. Two segments of transmission lines of the same electrical length with opposite signs are cascaded to provide zero phase at the operation frequency. The closed-form formulas for the equivalent circuit of a transmission line are used for circuit design. Both antenna layout and radiation mechanism are discussed. For experimental demonstration, the proposed antenna operating at 2.45 GHz was implemented on an FR4 substrate. The topology using several patches has quite smaller size than the conventional patch antenna. Besides, a fairly omnidirectional radiation pattern was measured.     

Full-wave analysis of microstrip floating-line discontinuities

A full-wave analysis of the resonance generated by a floating line is presented. Beginning with the dyadic Green's function for a dielectric slab, an integral equation is formulated. This integral equation is then solved by the method of moments in obtaining the transmission and reflection coefficients, as well as current distributions along the transmission line and on the floating line, both longitudinal and transverse. Employing these results, the near- and far-zone fields, as well as radiation patterns are computed. It was found that under resonance conditions the radiation power can exceed 13% of the feeding power, which may cause a potential problem in electromagnetic compatibility. Singularities involved in the Sommerfeld integrals are carried out by a novel pole extraction technique in conjunction with conventional folding methods. The new technique reduced the relative error of the singular integrals due to inaccurate pole position about one order in magnitude in comparison to the traditional approaches. To verify the new approach, a number of cases of open-ended transmission lines and gap discontinuities are examined. The results obtained from this method showed good agreement with those of previous publications     

Application of the two-dimensional Fourier transform to nonlinearwave propagation phenomena

A new technique based on the two-dimensional Fourier transform is presented and applied to the study of nonlinear wave propagation phenomena in one-dimensional, finite, nonlinear transmission lines. The technique permits determining the effects of nonlinearities and boundary conditions on the Fourier transform and identifying incident and reflected waves and solitons which may propagate through the transmission line at constant speed. The effects of windows on the Fourier transform are also assessed in both linear and nonlinear transmission line models     

一种计算无损传输线上电压、电流解析解的方法

直接求解无损传输线方程所得的通解包含了正向行波和反向行波两部分。本文在此基础上根据行波在传输线上多次反射的现象。推导出了在阶跃激励下无损传输线上任意一点的解析解,并对线上电压、电流的稳态值作了讨论。同时,该方法更加清晰地描述了线上电压和电流行波的暂态过程,更能体现出通解的物理含义。     

多回高压输电线路产生的无线电干扰分析

在规划设计，中关村软件园东侧将建设包括4回220kV四分裂导线，6回110kV单导线构成的10回高压输电线路，为了评估该高压线路走廊对软件园的电磁环境影响。在简述高压输电线路由于电晕产生的无线电干扰的基础上，分析单回220kV四分裂导线。220kV不采用分裂导线两种情况下的无线电干扰水平，由此估计该10回输电线路产生的无线电干扰水平，结果表明，该高压线路走廊产生的无线电干扰水平符合国家标准GB15707-1995《高压交流架空送电线无线电干扰限值》相应的要求。     

High-frequency electromagnetic field coupling to long terminatedlines

We present a theory for the EMC problem of electromagnetic field coupling to a long line with arbitrary terminations. The theory is applicable for the high-frequency plane wave electromagnetic field excitations, when the transmission line approximation is no longer valid. Analytical expressions are derived for the induced current along the line, and at the two-line terminals. The coefficients of these expressions are determined using a procedure based on the exact solutions of the integral equation for two similar line configurations, but having a significantly shorter length. The method is, therefore, particularly efficient when considering the electromagnetic field coupling to very long lines. The advantage of the proposed approach is that, in contrast with transmission line approximation, it takes into account high-frequency radiation effects. Furthermore, it allows a considerable reduction in computation time and storage requirements with respect to conventional numerical solutions based on the thin-wire approximation     

Power leakage, characteristic impedance, and leakage-transitionbehavior of finite-length stub sections of leaky printed transmissionlines

Power leakage and leakage transition phenomena in finite-length stub sections are studied for slot- as well as strip-type leaky transmission lines. A three-dimensional (3-D) method of moments is used for the rigorous analysis of the stub sections. The results reveal several important characteristics of power leakage in printed circuits that are not obtainable from the two-dimensional (2-D) analyses of ideal infinite-length lines. A new definition of the characteristic impedance for a leaky printed transmission line is proposed, which is shown to correctly model the impedance behavior of the finite-length sections. It is noted that the standard definitions of characteristic impedance, commonly used for nonleaky transmission lines, may not apply to practical circuits when leakage exists. Further, the leakage transition behavior in the finite-length sections, operated around a “mode-transition” region, is explained from the 3-D analysis results. Leakage analyses of ideal infinite-length lines can not model such transition excitation in finite-length circuits     

基于感知组织的输电线路结构识别方法

为了提高输电线路缺陷诊断正确率，有效降低各种复杂背景纹理及光线对识别输电线路结构的影响，从Gestalt感知理论着手，研究一种多感知识别输电线路结构的方法。在图像识别的底层，提取不同方向、不同宽度的线段，研究了一种融合计算Gestalt定律的近似性、连续性、共线性的多级搜索算法，获得显著的、完整的输电线路人造对象轮廓；在图像识别的中层，研究一种基于分块与合并的计算方法能视觉感知近平行线、近对称交叉的结构，设计了一个三级分类器感知聚类平行线组；在图像识别的高层，研究输电线路的知识模型，建立识别输电线路组成结构的约束机制，进而从语义上唯一地识别输电线路的结构。通过无人机巡检采集的输电线路图像，验证这种方法能有效识别输电线路组成的杆塔、导线、地线及绝缘子所在区域。     

Closed-Form Expressions for the Total Power Radiated by an Electrically Long Multiconductor Line

Two analytical solutions based on transmission-line theory for the total power radiated by a multiconductor line above a ground plane are proposed. The line is not assumed to be electrically short or close to the ground plane, thus making the proposed model suitable for assessing the emission/immunity of actual transmission lines employed in industrial contexts such as in the automotive domain, railway lines, and power-distribution lines. The model allows an imperfect ground plane to be considered through the complex-image approximation together with propagation losses. Numerical and experimental results are provided as a validation, while an empirical rule to assess the accuracy of the results is proposed. The two expressions aim at allowing fast parametric analysis of radiation during the design phase of the electrical and geometrical configuration of an unshielded multiconductor transmission line.      

Full wave characterization of a through hole via using thematrix-penciled moment method

A full wave analysis was presented in this paper for the propagation characteristics of a via which connects two semi-infinitely long transmission lines through a hole in a ground plane. The current distribution on the via and a section of transmission line became solved under the thin wire approximation by the moment method and the scattering parameters are extracted by the matrix pencil method. Numerical results were included to investigate the frequency dependent propagation characteristics for via structures with various geometrical parameters, e.g. the via height, wire diameter, and via hole radius. The radiation loss was shown from a comparison with the quasi-static model to become important if the via height is larger than one tenth of a wavelength. The radiation mechanism could be mainly attributed towards the associated wire antenna structure and, at rather high frequencies, towards the associated grounded via structure     

CAD-Oriented Model of a Coplanar Line on a Silicon Substrate Including Eddy-Current Effects and Skin Effect

Silicon technologies are now widely used for RF applications. Due to the substrate and conductor conductivity, losses and magnetic coupling affect the signal propagation in transmission lines. We propose an equivalent scheme for a transmission line taking these phenomena into account. All the parameters are analytically extracted from measurements. The magnetic coupling, including eddy currents, are described as series elements. They are affected by skin effects. The electric losses are described as parallel elements. They depend on the different layers that the electric field lines meet.     

Distributed equivalent sources for the analysis of multiconductortransmission lines excited by an electromagnetic field

The interaction of multiconductor lines with electromagnetic radiation is commonly studied in terms of field-induced voltage and current sources distributed along the line. The author presents the relationships between these sources and the incident fields for the general case of a transmission line with its conductors embedded in different dielectric volumes of arbitrary shape. It is shown that the sources can be expressed directly in terms of the incident fields and some vector parameters which are determined from the solution of a series of electrostatic problems with appropriate boundary conditions independent of the incident electric fields. It is noted that the multiconductor lines are suitable for direct applications in microwave transmission lines with rather arbitrary configurations     

Analysis of a slot microstrip antenna

The slot microstrip antenna is used as a folded slot dipole symmetrically fed across a gap by means of a strip line. A theoretical model equivalent to several lossy transmission lines had been described previously to explain the bandwidth and the radiation admittance. The theory is improved when coupling between the two equivalent radiating lines of every slot is taken into account, and explains a fourth resonance near the third one, which had been measured on several models. Theoretical results and experiments are in good agreement. They are radiation admittance in a wide frequency band, current distribution along each slot and radiation patterns.     

Full-wave analysis of radiation effect of microstrip transmission lines

A full-wave analysis of radiation effects produced by discontinuities in microstrip and buried microstrip transmission lines is presented. Beginning with the dyadic Green's function for a dielectric slab, with an embedded source, an integral equation is formulated. This equation is then solved by the method of moments to obtain the current distributions along the transmission line, in particular, near the discontinuities. Employing these results, the near- and far-zone fields, as well as radiation patterns are computed. The results from our method showed good agreement with those of previous publications in complex reflection and transmission coefficients, and equivalent capacitance values. It is found that under resonance conditions the radiation efficiency of a simple structure can exceed 41%, which may cause a potential problem in electromagnetic compatibility. Our analytic result also shows that the maximum radiation occurs when the source is located at the height of from the bottom ground plane, which should be prevented.     

Full-wave spectral-domain computation of material, radiation, andguided wave losses in infinite multilayered printed transmission lines

A unified solution for full-wave computation of losses in a general multilayered planar transmission line is presented. It includes material losses (dielectric and conductor losses), losses due to radiation leakage, and losses caused by leakage of power to source-free characteristic modes (surface-wave or waveguide modes, for example) of the multilayered geometry. A spectral-domain moment method is used with the Galerkin testing procedure. Significant modification of the conventional spectral-domain analysis of planar transmission lines is necessary in enforcing proper boundary conditions in the Galerkin testing procedure and, more importantly, in accounting for poles and branch cuts in the complex Fourier transform domain in order to rigorously account for the different loss mechanisms discussed. Results for a few representative geometries, namely, strip and/or material loss in a microstrip line and a slotline, surface parallel plate mode leakage loss in a conductor-backed slotline and a two-layer stripline, and radiation loss in a single and a coupled stripline at the interface between two infinite mediums, are presented to demonstrate these various loss effects