一种新型双侧漏泄同轴电缆辐射特性分析

为了解决室内5G 信号覆盖盲区的问题,对单侧漏泄同轴电缆进行了改进,设计了一种新型的双侧漏泄同轴电缆。根据周期结构的槽孔天线阵列理论,以电磁仿真软件Ansoft HFSS作为分析工具,建立双侧开槽的漏缆仿真模型,得到了电场分布、耦合损耗、方向图和S参数的特性;对不同节距和槽长进行仿真,获得了不同辐射模式下,漏缆耦合损耗随节距、槽长变化的曲线。研究结果表明:双侧漏缆比单侧漏缆的电场强度更均匀,方向图更加对称,通信质量更高,为5G信号在室内覆盖提供解决方案。     

Theory and analysis of leaky coaxial cables with periodic slots

Frequency band and coupling loss are the two important parameters of leaky coaxial cables with periodic slots. The frequency band can be predicted by analyzing the arrangement of the slots on the outer shield of the cable, but the coupling loss is not so easy to determine by classical methods. In this paper, the finite-difference time-domain (FDTD) method is used to calculate the electric field distribution in the slot cut in the outer conductor of the coaxial cable. The dyadic Green's function is then used to calculate the radiation field of the equivalent surface magnetic current densities. By these two methods, the coupling losses of the leaky coaxial cables with different periods, sizes and shapes of the slots can be accurately obtained. Some results in this paper were verified by the experimental results of leaky coaxial cables designed for railway mobile communications with a frequency band of 100-500 MHz     

Evaluation of edge effects in slot arrays using the geometricaltheory of diffraction

The geometric theory of diffraction (GTD) is applied to evaluate efficiently the coupling coefficient associated with the design of a waveguide-fed longitudinal shunt slot arrays. The coupling coefficient is proportional to the reaction integral between the field of a slot and the equivalent current distribution of another slot. Using an approximate form of the Green's function for the wedge, it is shown that the edge-diffraction field due to each slot is practically equal to the field of a suitable `mirror image' of such slot. In this way the actual coupling coefficient can be decomposed into a sum of coupling coefficients between slots on an infinite ground plane. The latter can be evaluated very efficiently so that inclusion of edge effects does not slow down the design procedure. The same approach also allows the computation of the relation between the self-admittance with and without the edge. Some test cases are provided which show that the overall error of this approximation can be neglected since it is comparable with the error due to mechanical tolerances     

微波脉冲与带缝非金属腔耦合的数值模拟研究

应用时域有限差分法(FDTD)模拟计算了微波脉冲与带缝非金属腔体的线性耦合过程.在正弦波凋制的高斯脉冲源激励下,分析了耦合场在腔体内的分布情况,总结了相对介电常数、腔壁厚度、孔缝尺寸等因数对耦合特性影响的基本规律.结果表明:在入射电场方向腔体中心轴线上的耦合场基本保持不变,垂直于入射电场截面上耦合场关于截画中心点呈对称分布;耦合进腔体的能量随厚度的增加和介电常数的增大而减小,但介电常数的影响更加明显,且随孔缝面积的增大而增大,面积一定时,随纵横比的增大而增大;孔缝中心处的电场耦合系数峰值随介电常数的增大呈近似线性下降,而腔体中心处呈振荡减小,在相对介电常数为6左右电场时域峰值达到最大;腔体内耦合磁场的变化规律与电场的类似.     

Analysis of a thin slot discontinuity in the reference plane of amicrostrip structure

This paper presents a perturbational approach based upon the spectral domain technique for the analysis of the discontinuity effects introduced by a thin slot in the ground plane of a microstrip line. The discontinuity problem is formulated in terms of the unknown slot field by using the notion of equivalent half-space problems, using a new rigorous procedure for deriving the TE-TM decomposition of the fields and equivalent transmission line models. The perturbation current on the infinite microstrip is computed once the electric field in the slot has been derived, and an equivalent circuit for the discontinuity is obtained from this perturbation current for the low-frequency regime. Computed results are presented and compared to the measured data     

Numerical analysis of centered-inclined coupling slots in rectangular waveguides

Numerical analysis is presented for the characteristic parameters of centered-inclined coupling slot in rectangular waveguides,taking into account the transverse distribution of the electric field across the slot aperture.Integral equations are formulated based on dyadic Green＇s function theories and solved using the method of moments.Trigonometric basis functions are adopted.It is found that the method will converge with up to ten basis functions.The characteristic parameters can be easily obtained for different slot sizes.Resonant length and resonant resistance of the coupling slots are calculated.It is shown that the calculated results have very high accuracy,compared with simulated results obtained from commercial software.Therefore,it can be effectively applied in the synthesis of antenna arrays.Effects of the transverse distribution on calculating resonant parameters of the coupling slot are also analyzed.The results show that if the transverse distribution of the electric field is neglected,the calculated error tends to become larger when the slot gets wider or thinner.     

Etude des perturbations induites par une décharge orageuse sur un câble de télécommunication

Experimental results presented in this paper show the waveform and magnitude of the interference signals that occur on a telecommunication cable located nearby a lightning discharge. The measurements were performed at Saint-Privat-d’Allier (France). We then study the current induced in the outer shield of aerial cables of several lengths and in the common mode voltages which appear on the load impedances. We also give a few results obtained from a buried cable. We will compare experimental results and theoretical predictions that are based on the computation of the electric field radiated by the lightning current and on the coupling of the electric field with the wire structure. This last point is approached through the transmission line theory.     

Analyzing electromagnetic pulse coupling by combining TLT, MoM, andGTD/UTD

An important problem in electromagnetic compatibility (EMC) analysis is to determine the coupling of an electromagnetic field into a shielded cable. Using the transmission line theory (TLT), the disturbance voltage induced inside the cable is easily calculated from the current distribution on its shield. This current distribution depends on the incident electromagnetic field and is efficiently determined by the method of moments (MoM). Extending the MoM with the geometrical and uniform theory of diffraction (GTD/UTD) makes it possible to solve scattering problems that are too large and too complex for the plain MoM. The combination of the three approaches-TLT, MoM, and GTD/UTD-allows calculation of the disturbance voltage inside a shielded cable, which is part of a complex scattering structure. The fundamentals of each method and the way of putting them together are shown in this paper. The application of the proposed method is demonstrated by an example: the pulse coupling between a monopole antenna and a shielded cable is analyzed, taking into account a large conducting structure in the vicinity     

基于地-线缆耦合的感应电流分析*

高功率、大强度电磁波照射,是飞机在电子对抗中实施电磁干扰的重要手段。在实验室通过电流钳对线缆进行电流注入,从而达到模拟飞机系统间电磁干扰试验的目的。如何从理论上分析照射场在电缆上所感应的电流,是飞机系统间抗扰度实验的重要环节。文章利用有源传输线理论,建立了线缆-大地耦合模型,给出了线缆电流分布与大地电导率、地-线缆高度、线缆长度、线缆两端阻抗以及照射场的频率、幅度等多参数的关系;同时还进行了实测验证。结果表明,理论分析与实测结果基本一致,这为飞机系统间电磁干扰试验的实施提供了必要的理论和数据基础。     

Scattering from cavity-backed apertures: The generalized dual series solution of the concentrically loadedE-pol slit cylinder problem

The generalized dual series solution to the scattering of anE-polarized (E-pol) plane wave from an infinite circular cylinder having an infinite axial slot and enclosing an infinite concentric impedance cylinder is presented. This solution explicitly exhibits the correct edge behavior, and it can handle cylinders that are either electrically small or large without special considerations. The angle of incidence is arbitrary. A variety of current, field, and cross-section results are presented. These are compared with the correspondingH-pol problem results to establish the polarization dependencies of the aperture coupling. It is also shown that effects corresponding to the presence of the interior cavity dominate all of the scattering data. In particular, the bistatic cross sections in either case and the current induced along an interior wire in theE-pol case exhibit new resonance features that are due to the cavity-backed nature of the aperture.     

Backscattering from an impedance loaded slotted cylinder

When a thick infinite cylinder is illuminated by a plane wave with a perpendicular electric field at normal incidence, its backscattering can be controlled by implementing an impedanced-backed longitudinal slot on its surface. An exact theory is developed to account for the scattered field from an impedance loaded slotted cylinder. Optimum slot loadings for minimizing and maximizing the backscattering from the cylinder are determined. A series of experiments has been conducted to verify the theory. Excellent agreement between theory and experiment is obtained. The present study indicates that a very effective reduction in the backscattering from the cylinder can be achieved by a proper design of the slot loading.     

ESD field penetration through slots into shielded enclosures: atime domain approach

This paper presents a time domain approach for the analysis of the coupling between an electrostatic discharge (ESD) current and the internal region of a shielded enclosure with a slot. The application of the equivalence principle allows us to obtain an integro-differential equation for the unknown distribution of the aperture electric field. The numerical solution is obtained by an iterative procedure developed by the method of moments (MoM) in the time domain. The approach is also applied at the case of a transient incident field of a plane wave impinging on the enclosure. The use of proper impulse responses for the space and cavity regions make the model efficient from a computational point of view, without loss in accuracy. Theoretical results are validated by measurements     

Radiation from a two-dimensional array of coupled slot lines

The problem of radiation of the eigenmodes of an infinite 2D array of semi-infinite coupled slot lines is solved. An analytical solution for the electric field on conductors is found by the Wiener–Hopf method in the approximation of narrow conductors forming the slot lines. An algorithm of numerical implementation of this solution is developed. Expressions for elements of the scattering matrix of an infinite array are found. Dependences of the elements of the scattering matrix on frequency and the structure parameters are studied numerically.     

Dependence of induced transmembrane potential on cell density,arrangement, and cell position inside a cell system

A nonuniform transmembrane potential (TMP) is induced on a cell membrane exposed to external electric field. If the induced TMP is above the threshold value, cell membrane becomes permeabilized in a reversible process called electropermeabilization. Studying electric potential distribution on the cell membrane gives us an insight into the effects of the electric field on cells and tissues. Since cells are always surrounded by other cells, we studied how their interactions influence the induced TMP. In the first part of our study, we studied dependence of potential distribution on cell arrangement and density in infinite cell suspensions where cells were organized into simple-cubic, body-centered cubic, and face-centered cubic lattice. In the second part of the study, we examined how induced TMP on a cell membrane is dependent on its position inside a three-dimensional cell cluster. Finally, the results for cells inside the cluster were compared to those in infinite lattice. We used numerical analysis for the study, specifically the finite-element method (FEM). The results for infinite cell suspensions show that the induced TMP depends on both: cell volume fraction and cell arrangement. We established from the results for finite volume cell clusters and layers, that there is no radial dependence of induced TMP for cells inside the cluster.     

Backscatter RCS for TE and TM excitations of dielectric-filledcavity-backed apertures in two-dimensional bodies

Transverse electric (TE) and transverse magnetic (TM) scattering from dielectric-filled, cavity-backed apertures in two-dimensional bodies are treated using the method of moments technique to solve a set of combined-field integral equations for the equivalent induced electric and magnetic currents on the exterior of the scattering body and on the associated aperture. Results are presented for the backscatter radar cross section (RCS) versus the electrical size of the scatterer for two different dielectric-filled cavity-backed geometries. The first geometry is a circular cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the cylinder is dielectric filled and is also of circular cross section. The two cylinders (external and internal) are of different radii and their respective longitudinal axes are parallel but not collocated. The second is a square cylinder of infinite length which has an infinite length slot aperture along one side. The cavity inside the square cylinder is dielectric-filled and is also of square cross section     

Transmission Line Mode Response of a Multiconductor Cable in a Transient Electromagnetic Field

This paper describes a technique for obtaining the induced worst case currents on individual wires of a multiconductor cable as a result of a transient electromagnetic radiation field. The technique involved a development of the expression for the induced current in matrix form where the mutual coupling terms and the other cable currents are the pertinent parameters. A worst case solution results from the assumption of maximum coupling orientation of the individual wires. A short example and some test results are presented. The test results show wave shapes for inductive and capacitive coupling. The solution for the individual wire current due to a transient electromagnetic field is important, since it will greatly reduce the required number of cable measurements and will allow the development of improved shielding techniques.     

Modeling of magnetic-field coupling with cable bundle harnesses

A field-to-line coupling model is developed for cable bundle harnesses in terms of the scattering currents and total line voltages. The equivalent distributed sources representing the effects of electromagnetic coupling are expressed as a function of the incident magnetic-field components. Such a formulation is particularly suitable to be used for the analysis of multiconductor transmission lines excited by a transient field, when data for the incident electric field are either inaccurate or not available. This model allows the accurate calculation of the induced voltages and currents on complex cable bundles. The effects on the induced voltages and currents due to ground losses and to the presence of the dielectric sheath in shielded and unshielded cables is discussed, considering bundles excited by either slow or fast transient fields. Numerical applications demonstrate the validity of the proposed procedure.     

The heart of a new machine [Powerformer, cable-wound statormachine]

Powerformer (an amalgam of power generator and transformer) is a radically new generator design that could herald a new era in high-voltage generation. The new machine from ABB is a 100 RPM, 11 MVA, 45 kV machine, installed as unit 9 (U9) of the Porjus Hydropower Centre, on the Lule river in northern Sweden. The Powerformer uses a cable-wound stator using XLPE insulated cable. The cable's circular cross section solves the two basic problems arising from the use of conventional, rectangular stator windings. First, within the stator slots, the uniform field in the insulator maximises insulation performance, and hence the voltage rating of the cable. Secondly, bending a cable of circular cross section does not result in the kinks and sharp edges that arise with a rectangular cable. Thus, even in the end regions, where the cable is bent to make the transition from one slot to the next, the electric field within the insulator remains free of singularities. In the end regions of the Powerformer the electric field remains confined within the cable, and the need to control an external electrical field as in a conventional machine, is eliminated     

Calculation of electric fields in a multiple cylindrical volume conductor induced by magnetic coils

A method is presented for calculating the electric field, that is induced in a cylindrical volume conductor by an alternating electrical current through a magnetic coil of arbitrary shape and position. The volume conductor is modeled as a set of concentric, infinitely long, homogeneous cylinders embedded in an outer space that extends to infinity. An analytic expression of the primary electric field induced by the magnetic coil, assuming quasi-static conditions, is combined with the analytic solution of the induced electric scalar potential due to the inhomogeneities of the volume conductor at the cylindrical interfaces. The latter is obtained by the method of separation of variables based on expansion with modified Bessel functions. Numerical results are presented for the case of two cylinders representing a nerve bundle with perineurium. An active cable model of a myelinated nerve fiber is included, and the effect of the nerve fiber's undulation is shown.     

Research on the Radiation Characteristics of Patched Leaky Coaxial Cable by FDTD Method and Mode Expansion Method

Patched leaky coaxial cable (PLCX) is proposed as an alternative to the conventional leaky cable for wireless links in a complex environment. It is expected to have the capability of adjusting the coupling between the cable and the environment and give smoother electric field coverage. In this paper, the radiation characteristics of the PLCX with general inclined patches are studied by a hybrid method that involves the finite-difference time-domain (FDTD) method for the near-field computation and the mode expansion method for the transformation of near field to far field. In the method, the space around the patched leaky cable is divided into two regions by an artificial closed cylindrical surface that is incorporated with the FDTD lattice surface when implementing the FDTD iteration. The field distribution on the artificial surface is obtained after the implementation of the FDTD method. Meanwhile, the field outside the artificial boundary is expanded in terms of the Floquet modes with coefficients to be determined. By matching the field expressed by modes and the field obtained from the FDTD method at the artificial boundary, a matrix equation with unknown coefficients is obtained. Solving this matrix equation, the expansion coefficients are known, and the field outside the artificial boundary is ready to be obtained.