漏泄同轴电缆的性能参数及其影响因素的研究

本文介绍了漏泄同轴电缆的类型和漏泄原理,以双八字槽漏泄同轴电缆为例．分析和讨论了漏泄同轴电缆的主要性能参数及其影响因素．为漏泄同轴电缆的设计工作提供了参考依据。     

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     

铁路无线通信用漏泄同轴电缆设计

介绍了周期性开槽漏泄同轴电缆的主要电气特性及其相互关系,从理论上分析了影响主要电气特性的因素。采用全波仿真方法,探索了八字形漏泄同轴电缆的槽孔倾斜角度和长度对其电气性能的影响,设计了一种周期性八字形槽的某型漏缆,测试结果与仿真结果吻合,满足铁路通信漏泄同轴电缆标准要求。     

Guided radiation by coaxial cable for train wireless systems in tunnels

In railway radio systems and vehicular communications, a very important problem is that of maintaining stable communications at all locations, especially in tunnels and in spaces between buildings. A leaky coaxial cable having a new type of slot as a radiating element combining longitudinal slots with circumferential slots is described, and the desired radiation power or coupling loss can be easily designed by varying the dimensions of the slots and by selecting an appropriate pitch length. The results of the experimental studies at a frequency of 450 MHz are expected to give a satisfactory solution to this problem.     

3GHz宽带“八”字槽漏泄同轴电缆的设计及性能

3GHz宽带漏泄同轴电缆的设计要求是在3GHz宽带频率范围内所有使用频段都具有有效的传输距离（衰减）及良好的辐射特性（足够的耦合损耗及均匀的全向辐射场强图）。通过外导体“八”字槽孔结构参数的设计调整,研制出在3GHz所有的通信频率中均能使用,并具有优良性能的辐射型漏泄同轴电缆。     

Electromagnetic Field Analysis for a Coaxial Cable with Periodic Slots

The analysis deals with the excitation of coaxial structures with periodic apertures in the outer cylindrical shield. These apertures are taken to be finite circumferential slots of thin width. A quasistatic method is employed that reduces the problem to a field matching of angular wave functions over the angular extent of the slots. An approximate averaging technique is then used to obtain expressions for the effective admittance of the cable. It is then argued that this can be used to characterize the cable in more complicated environments.     

Propagation on a Ported Coaxial Cable Buried in Flat Earth

Consider a horizontal coaxial cable with periodic slots in the outer conductor. This ?leaky cable? is buried in the earth as one component of an intruder detection system. We develop the theory for surface-wave propagation on the cable in the presence of the planar air-earth interface. Numerical results are included for the phase velocity and attenuation constant as functions of the various parameters. Data are presented for the electric-field strength at the air-earth interface, and the electric-field distribution in the air region above the buried cable.     

Radiation of a Leaky Coaxial Cable With Narrow Transverse Slots

The problem of a leaky coaxial cable with narrow transverse slots is solved by using the Fourier transform and mode-matching techniques. The characteristics of far-field radiation and near-field coupling are presented in terms of numerically fast convergent series. Our theoretical results are compared with experimental data to confirm favorable agreement     

Radiation properties of circumferential slots on a coaxial cable

Both the Galerkin's and mode-matching methods are used to analyze the reflection and radiation properties of a coaxial cable with a circumferential slot on the outer conductor. The effects of higher order modes are also included. The accumulated effect of multiple slots on the reflected signal is also studied by using a Monte Carlo simulation     

八字形槽漏泄同轴电缆耦合损耗仿真分析

广泛应用于地铁、隧道、地下商场、矿井等闭域空间的漏泄同轴电缆,因不同应用环境对其电气性能要求不同,因此分析影响漏泄同轴电缆耦合损耗等电气性能的因素、探索其变化规律,具有重要的工程应用价值。文中分析了八字形槽孔漏泄同轴电缆耦合损耗随槽孔角度、长度和槽孔节距的变化规律,提出保持单八字形槽孔对几何结构参数不变,仅改变相邻八字形槽孔对之间距离的槽孔节距调节方法。给出了采用此种方法的实际设计算例,仿真结果与实测结果吻合。     

Coaxial-slot surface-wave launcher

The use of an array of circumferential slots in the outer conductor of a dielectric-clad coaxial cable as a new way to launch a TM0 surface wave on a Goubau line is described. Its advantage over a conical horn lies in its efficiency depending only on its length, which makes it particularly suitable for use in a high-speed ground transportation system.     

基于DSP的超柔同轴电缆轧纹机控制器

随着移动通信的快速发展,基站用超柔同轴电缆的用量也在迅速增加。超柔射频同轴电缆比普通同轴电缆要求更高的弯曲特性。根据超柔同轴电缆的结构特点和传输特性,设计并研制了生产超柔同轴电缆的基于DSP的轧纹机控制器。该控制器采用TMS320VC5410作为信号处理器,用TLC320AD50C作为A/D输入和D/A输出单元。介绍了该控制器的工作原理、硬件电路和软件结构。实践表明,该控制器具有良好的动态特性和可靠性。     

基于电容加载的宽带小型化扼流结构的设计与研究

设计并研究了基于电容加载的宽带小型化扼流结构来抑制同轴线外导体表面的寄生电流。提出了能定量分析其扼流效果的通用性方法。此扼流结构与同轴线外导体相连,由两侧对称I型开缝的金属板组成,并在缝隙处加载电容使其实现小型化。其工作原理等效于一组串联的LC电路,当同轴线外导体外表面存在有寄生电流时,扼流结构的高阻抗特性会在一个宽频带内抑制电流的传导。该文对扼流结构的特性原理及理论基础进行了研究,结果表明此扼流结构能在5250~5925MHz范围内对寄生电流的传输特性有-12d B的抑制性能。     

Bloch Wave Analysis of Long Leaky Coaxial Cables

Leaky coaxial cables can be used as distributed radiators for indoor communications. When the number of slots is large, as it is often the case, the application of a full-wave analysis method is very demanding in terms of both memory and CPU time. In this paper an analysis technique, based on Bloch wave theory is presented. Slots are viewed as discontinuities in an open waveguide and a suitable basis of orthogonal polynomials is introduced to represent the modal amplitudes pertaining to the continuous spectrum. The radiation properties of the cable are discussed in detail in terms of the excited Bloch waves. Finally, the reflection coefficient at the junction between a uniform and a slotted cable is computed. The results are presented in the form of a chart, for general slot size and spacing.     

Submarine Coaxial Cable Pressure Characteristics

In equalization design of submarine coaxial cable system, the cable attenuation deviation due to pressure in deep sea bottom has significant weight. This paper treats the submarine coaxial cable characteristics pressure dependency. By using an artificial ocean test facility, 1.7 inch submarine coaxial cable attenuation, phase, capacitance and insulator core diameter were studied and their pressure coefficients under a pressure of 0 to 500kgw/cm^{2}at temperatures of 5, 10 and 20°C were obtained. In this study, pressure dependence of polyethylene dielectric constant and dissipation loss were quantitatively analyzed. The attenuation pressure coefficient varies with frequency. For example, cable attenuation in the sea at a depth of 5000 meters is higher than that on the land by 1.09 percent at 10 MHz and by 1.54 percent at 60 MHz at a temperature of 10°C.     

Accurate modeling of metal plate-loaded loop-coupled cavities withslots

In this work, we analyze the problem of the electromagnetic field radiated from apertures in coaxial fed metal enclosures loaded with metal inserts. Such situations are found, for example, in PC environments where slots and apertures are used for the purpose of heat dissipation, CD-ROMs, cable penetration etc. We derive an accurate model of the entire structure, including the coaxial line-to-loop-to-cavity feed and the inner metal planes, simulating the presence of the circuitry inside. The analysis is developed by means of the hybrid transmission line matrix-integral equation (TLM-IE) method and theoretical results are compared with experimental ones showing very good agreement. The evaluation of the reflection coefficient and of the level of radiated emission as functions of the metal plates position is very helpful toward the engineering design of the entire structure. The numerical simulations require rather low computational effort     

Magnetic Field Pickup by Flexible Braid Coaxial Cables

Cabling systems have long been known to be a source of unwanted pickup of radio-frequency interference. A typical source of pickup occurs when the outer sheath of a coaxial cable system forms part of a ground return for potentially interfering electromagnetic energy. Another source of penetration arises from a magnetic field which is perpendicular to the axis of the coaxial cable. A previous study demonstrated that the field emanating from a coaxial cable could be characterized as an equivalent open-wire pair. This particular effect is caused by the eccentricity between the centers of the outer and the inner conductors or because of other asymmetrical characteristics. The susceptibility of a coaxial cabling system to perpendicular magnetic fields can also be characterized in terms of an equivalent open-wire pair for short runs. The purpose of this investigation was to measure the shielding effectiveness of a typical flexible braid coaxial cable to magnetic fields perpendicular to its axis and to demonstrate that a coaxial cable may be considered as an equivalent open-wire pair in a cylindrical shield. A test setup employed a parallel plane transmission line to generate a uniform magnetic field perpendicular to the axis of the coaxial cable. The shielding effectiveness of the braid was measured for several classes of braid conditions. Then, using the same braid, a coaxial cable with an experimentally induced known eccentricity was employed and the overall pickup measured. The results confirmed the objectives of the investigation.     

Numerical analysis of the propagation characteristics of multianglemultislot coaxial cable using moment method

In this paper, multiangle multislot coaxial cable is analyzed qualitatively and quantitatively. This is the extended result of the previous studies of the single-slot coaxial cable. The properties of this cable have been studied by many authors, especially for the surface-wave type. However, the slotted coaxial cable utilizing leaky waves has not been treated rigorously despite its wide use. In this paper, a numerical analysis of a leaky coaxial cable with a multiangle multislot configuration is performed to obtain many useful results, which are impossible to derive employing the approximate model frequently used in this area. Using the moment method, the propagation constant has been obtained for the leaky coaxial cable as a function of various parameters. Several slot configurations are considered to give insight into the properties of coupling loss and transmission loss complicated by simultaneous existence of leaky and surface waves     

基于自适应遗传算法的寄生电流抑制结构设计与研究

为了抑制同轴线外导体表面存在的寄生电流，设计并研究了基于自适应遗传算法的寄生电流抑制结构.该结构是一个与同轴线外导体相连且两侧有五对对称I型开槽的金属板，在开槽处加载集总电容以实现小型化要求.该结构工作原理可等效为一组串联LC谐振电路，当有外部因素导致同轴线外导体表面有寄生电流存在时，该等效电路呈现的高阻抗特性会抑制寄生电流的流经.为了选取合适的电容，提出了一种自适应遗传算法来优化计算加载电容的大小，该遗传算法实现了交叉率和变异率的非线性自适应调整，与标准算法相比，该算法有更优的收敛速度以及鲁棒性.利用此算法完成了相应的计算和分析，结果表明该结构能够在5 250~5 925 MHz范围内对寄生电流实现-10 dB以上的抑制效果.本文方法能够指导寄生电流抑制结构设计，并进行寄生电流抑制效果的定量分析.     

传输 0.1THz 的微尺寸同轴电缆的优化设计

随着太赫兹技术的发展,人们对低损耗THz 传输器件的需求越来越迫切。在本文中,提出了一种利用光子晶体 光纤制备技术来实现的微尺寸同轴电缆的优化结构设计。这种优化设计的结果可以使成份为石英和铜组成的微尺寸同轴 电缆对0.1THz 的损耗降到5.45dB/m。