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。     

漏泄通信系统在地铁中的应用

地铁内信号的覆盖问题始终困扰运营商,目前行之有效的方法是搭建一套漏泄通信系统.此系统首先应用合路平台设备(POI)技术;其次采用漏缆传输方式对地下空间进行信号覆盖;再次通过有线方式将各运营商的信号传送到地铁站内的各自基站,系统信号经POI合路后通过地铁内的漏缆把信号发送出去,从而实现地铁内信号的覆盖.最后将研究成果应用到某运营商地铁线路的网络建设中,为后期地铁无线网络设计提供了思路.     

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.     

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。     

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     

Leaky coaxial cable characteristics at 900 MHz

Mobile communication through electromagnetically obstructed areas can be established by using wayside leaky coaxial cables. Available experimental data had been limited to 450 MHz. This paper presents the results of a recent experiment of the RADIAX cable at 900 MHz in near-field. These data are used to supplement an earlier RADIAX experiment at frequencies below 450 MHz and to compare with a theoretical study at 1 GHz.     

等效电路法研究漏泄同轴电缆传输和耦合特性

研究了以埋地漏泄同轴电缆作为分布式传感器的电气特性，拟应用于隧道、铁路沿线等防止入侵破坏和预警山体塌方信号的探测.以垂直开槽漏缆结构为例，利用HFSS搭建全波仿真模型，理论分析并提取出缝隙的等效电路模型，从而以该模型为基础分析漏缆的传输、反射和耦合特性.从等效电路模型出发，运用ABCD矩阵计算出了等效电路模型中的电路参数值及漏缆间耦合参数值.理论计算与全波仿真非常吻合，验证了等效电路的正确性.结果表明，与HFSS仿真相比，本文提出的等效电路方法占用计算资源较少且大大缩减了仿真时间，解决了HFSS仿真漏缆长度受限及耗时太长的难题；同时理论计算出了等效参数值和漏缆间耦合参数值，更直观反映了漏缆间的耦合特性.     

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。     

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.     

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。     

SPICE-like models for the analysis of the conducted and radiated immunity of shielded cables

The aim of this work is the development and validation of compact SPICE models suitable to analyze the conducted and radiated immunity of shielded cables. The reference structures are coaxial cables, and shielded cables with two parallel wires (i.e., twinax cable). The conducted and radiated immunity of the shielded cables are evaluated considering as source a known injected current on the cable shield, and the coupling with an external plane wave electromagnetic field, respectively. The circuit models are validated by comparing the results with those obtained by other approaches. The developed models are then used to quantify the main grounding practices of shielded cables.     

一种基于脉冲压缩的漏缆传感器定位新方法

漏缆传感器的入侵探测定位系统已广泛应用于国防设施、银行、监狱等重要区域,为提高这种系统的定位精度,提出了一种基于脉冲压缩的漏缆传感器探测定位新方法。该方法将巴克码调制的二进制相移键控信号引入系统作为发射信号,并对接收信号进行滤波相减、相干解调、抽样判决和自相关运算等一系列信号处理,以获得含有入侵位置信息的特征信号。应用MATLAB 和电磁仿真软件CST 对该系统进行了协同仿真分析,并搭建了实验系统进行测试。仿真结果与实测结果吻合良好,验证了新方法探测定位的有效性。新方法的定位精度约为0.9 m,优于目前已报道的同类探测定位系统的定位精度。     

Design of a tunnel relay system with a leaky coaxial cable in an 800-MHz band land mobile telephone system

System design of a tunnel relay system in an 800-MHz band land mobile telephone system is described. Several dozen RF signals from a base station or many different mobile units in the tunnel are directly amplified in the RF stage, without frequency conversion, by a common amplifier in the relay equipment installed near the tunnel entrance, then radiated into the tunnel through a leaky coaxial cable (LCX) or to the base station by a unidirectional antenna. Repeaters are inserted along the LCX to compensate for transmission loss in RF signal power inside the cable. Amplifying a number of RF signals simultaneously, a common amplifier generates intermodulation products and radiates spurious signals. The required amplifier linearity to suppress the spurious signals is discussed in detail. The combination of LCX and service area in the tunnel is determined according to the amplifier performance, the number of radio channels assigned to the base station, and the radio wave propagation characteristics in the tunnel.     

A 270-kb/s 35-mW modulator IC for GSM cellular radio hand-heldterminals

The modulator IC is a mixed analog/digital transceiver component in a chip set that is designed for the hand-held terminals of the pan-European 900-MHz Groupe Special Mobile (GSM) digital cellular radio network. The concept of the radio-frequency environment in which the circuit is used is explained, focusing on the differences in existing systems. The architecture and different functions of the modulator circuit and details of the digital and analog processing in the transmission mode are discussed. The receiving mode, which is mostly based on analog processing, is highlighted. The device generates Gaussian minimum-shift-keying (GMSK) modulation and converts the received signal to 8-b words after filtering. The modulator IC uses digital waveform generation and a quadrature signal representation. This device is implemented in a 1.5-μm CMOS technology. The power consumption is less than 35 mW from a 5-V supply     

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.     

Comparative Testing of Leaky Coaxial Cables for Communications and Guided Radar

Leaky coaxial cables are finding increasing use in communications systems involving mines, tunnels, railroads, and highways, and in new obstacle detection, or guided radar, schemes for ground transportation and perimeter surveillance. This paper describes the theory and operation of a new laboratory testing technique for these leaky cables based on a novel form of cavity resonator. The technique yields highly consistent and repeatable results that usefully assist in the prediction of the performance of full-size systems, from a simple test on a small sample of cable in a laboratory setting.     

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。     

Underground use of a coaxial cable with leaky sections

The optimum efficiency of a leaky cable as a support for radio communications in tunnels involves a compromise between high leakage fields and a low increase of the coaxial mode attenuation. The latter is an important disadvantage of continuous leaky feeders. To obviate this, short leaky sections can be inserted in an otherwise well-shielded coaxial cable. These sections act as mode converters or radiators. A theoretical analysis based on coupled line theory enables us to determine the optimum characteristics of the leaky sections. Numerous experiments were carried out in a tunnel at various frequencies, using different lengths and characteristics of the leaky sections.     

基于无线通信的CBTC研究综述

对基于通信技术的列车控制系统进行了全面研究,分析了CBTC系统通过车地设备间的连续、高速、双向的数据通信技术,实现列车的高精定位和控制的关键作用,并进一步介绍了CBTC的基本原理、特点和系统结构,对CBTC系统中几种常用的无线通信解决方案进行了分析和比较,总结得出采用漏泄同轴电缆和无线电台混合组网的最优解决方案,同时指出CBTC系统由于采用了先进的通信技术,其必将引领现代城市轨道交通与铁路通信信号发展的未来方向.     

SYV-75—5和SWV-75—5同轴电缆在视频传输中的性能比较分析

SYV75—5和SYWV75—5是两种传输视频信号的同轴电缆,从理论上讲SYV75—5是用于监控系统的视频信号传输,SYWV75—5是用于有线电视的视频信号传输,然而在实际工程中有的工程商却用SY—WV75—5的线缆做视频传输。两种线缆的价格之差影响到工程造价,因此两种线缆在实际工程中能否替换的问题是值得探究的。通过理论分析与实际测试,论证SYV75—5和SM5—5两种同轴电缆在视频传输线路中的性能优劣,由此得出两种线缆正确的选用方法。