Role of controlled mode conversion in leaky feeder mine communication systems

Using an idealized model, we consider VHF wave transmission in a straight mine tunnel that contains a braided coaxial cable. The controlled interchange of energy between the propagation modes can be used to optimize the communication range and allow for coupling to and from portable hand-held antennas. In particular, we show that the optimum lengths for maximum transmission through the leaky cable sections or mode converters predicted here are compatible to those predicted by approximate coupled mode theory.     

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。     

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     

Propagation at 2.0 GHz in an Enclosed Area Using a Coaxial Cable with Leaky Sections as the Transmitting Antenna

This paper presents the results of narrowband and wideband propagation measurements carried out at 2.0 GHz in a large enclosed area using a coaxial cable with leaky sections as the transmitting antenna. The narrowband measurements were devised to measure attenuation of radio signals and the wideband techniques to measure multipath impulse responses and their associated root mean square delay spread. Analysis of the narrowband data files shows that the received signal levels in the direction parallel to the cable generally decay and display peaks in front of leaky sections due to the specific attenuation and special structure of the cable. The received signal levels in the direction radial to the cable decrease slowly and the distance-power law exponent is found to be slightly larger than one. The slow and fast variations of the received signal levels are also examined. The results reveal that the slow variations do not follow the lognormal distribution, while the fast variations fit the Rayleigh distribution in both parallel and radial directions. Analysis of the wideband data files yields that the maximum value of the root mean square delay spread is 86.1 ns and the root mean square delay spread values are less than 55 ns 50% of the time. One therefore can conclude that the enclosed area channel excited by the coaxial cable with leaky sections has a broad coherent bandwidth and can support the data rate up to 2.3 Mb/s without equalization.     

带漏泄段同轴电缆激励的2GHz无线电波在大型封闭区域内的传播

本文给出了在大型封闭区域,用带漏泄段的同轴电缆作为发射天线时,2GHz窄带和宽带无线电波传播特性的测量结果,对于窄带信号、主要测量了传播过程中的衰减,测量结果表明,在平行于电缆方向上,接收信号的电平比垂直于电缆方向的电平大;接收信号的快衰落服从瑞利分而,而慢衰落不服从正态分布。对于宽带信号,测量了多径脉冲响应,得到了均方根时延扩展及其概率分布。     

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。     

圆形隧道中泄漏同轴电缆辐射场的FDTD 分析

随着泄漏同轴电缆在各种闭域空间中的应用越来越广泛,其精确的辐射特性数值解也引起人们的关注。在圆柱坐标系下,根据泄漏同轴电缆的辐射理论,分析了圆形隧道中电磁波的传播途径,用时域有限差分（FDTD）方法求解了泄漏同轴电缆在圆形隧道中的辐射场。该方法相比于解析法,简化了计算程序,提高了结果的精确度,并且易于实现。 仿真结果表明在圆形隧道中,泄漏同轴电缆不存在传统天线所具有的通信盲区的缺点,可以实现与外部空间的全方位双工通信。     

Mode conversion by tunnel nonuniformities in leaky feeder communication systems

Using an idealized theoretical model, the inadvertent mode conversion between the bifilar and monofilar modes are dealt with in a tunnel that contains a braided coaxial cable. The tunnel is allowed to have various kinds of lateral nonuniformities such as changes of wall conductivity and permittivity. We conclude that such effects are very important in understanding leaky feeder systems.     

漏泄同轴电缆单模频带扩展的研究

从理论计算出发,进行了漏泄同轴电缆单模频带扩展的理论研究,提供了两种不同开槽的漏泄同轴电缆频带扩展的方式和理论支持,并将垂直开槽的频带扩展方式应用于实践,设计的样品经检测证明,此种漏泄电缆频带扩展的方法是完全可行的。     

耦合型漏泄同轴电缆传输和耦合特性研究

针对泄漏同轴电缆作为分布式传感器应用于物联网和智能家居的室内安防入侵检测时，运用全波仿真软件HFSS不能有效仿真长距离的耦合漏缆的问题，提出了一种等效电路模型.利用参数提取软件，先提取单个开槽的缝隙单元的等效电路模型，然后借助于传输线理论，利用四个传输矩阵级联得到整段漏泄同轴电缆的传输矩阵.并考虑两根漏缆缝隙间相互耦合，提出了表征耦合特性的等效电路模型.将等效电路模型利用商用软件高级设计系统（advanced design system，ADS）进行电路搭建与仿真.仿真结果表明，本文提出的两根漏缆的等效电路模型与全波仿真结果非常符合，可以快速地仿真长距离的耦合漏缆结构，并大大节约了仿真时间.     

U形漏泄同轴电缆的设计与实现

为达到某移动通信系统对漏泄同轴电缆主要电气指标的要求,设计一种U形漏泄同轴电缆,以满足工程应用。阐述了漏泄同轴电缆耦合损耗和传输衰减两个重要电气指标,以U形漏泄同轴电缆实例,利用三维电磁仿真软件HFSS仿真分析900 MHz工作频率下节距及槽孔尺寸的变化对耦合损耗、传输衰减的影响,仿真结果与实测结果吻合良好。结果表明U形漏泄同轴电缆节距越小,漏泄同轴电缆耦合损耗越小。     

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。     

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.     

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。     

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     

疏编织漏泄同轴电缆空间场分布的研究

通过对SLYWV-75-10型疏编织漏泄同轴电缆的空间场分布进行实际测量,并对测试结果和数据进行分析,证明SLYWV-75-10型疏编织漏泄同轴电缆完全能够作为户外周界入侵探测报警系统的探测传感器,同时对电缆间距、最大单元警戒范围以及系统的响应时间等给出了具体的参考指标,对户外周界入侵探测报警系统的研制和开发具有重要指导意义.     

A Feasibility Study to Monitor Soil Moisture Content Using Microwave Signals

A buried leaky coaxial cable is used as a sensor to continuously monitor the average moisture content of irrigated soil at a desired depth. The two-phase feasibility study consists of an analytical and an experimental investigation. The modal equation in the cable is expressed in terms of the surface impedance at the inner conductor boundary and an effective surface impedance at the outer leaky conductor boundary. The effective surface impedance is related to the soil moisture content through its measured attenuation. The results of the experimental work condncted in the field are in good agreement with the analytical results. It is shown that the recorded phase difference between the test signal from the buried cable and the reference signal can be used to monitor the soil moisture content.     

漏泄同轴电缆耦合损耗特性评定的探讨

除长度耦合损耗(Lc,50、Lc,95)值外,增加Lc,95-Lc,50值、天线三向Lc,95值、Lc,95耦合损耗圆图及其不圆度参量,扩展了IEC标准中的"耦合损耗",全面评定漏泄同轴电缆辐射电场特性。实例分析讨论不同结构漏泄同轴电缆辐射电场特性。     

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.