有缺陷同轴电缆的时域反射特性及应用

Time domain reflectometry property of defective coaxial cable and its applications

针对同轴电缆时域反射系统(TDR)在监测边坡变形中的应用,提出了同轴电缆时域反射测试系统的模型.在此基础上研究了不同特性阻抗同轴电缆系统的电磁波传播模型.通过室内试验,研究了国内最常见的三种同轴电缆发生剪切变形时的时域反射特性.在对多阻抗变化面同轴电缆传输系统的反射特性及同轴电缆剪切变形对TDR波形影响的计算及试验分析的基础上,总结了三种型号同轴电缆剪切面处特性阻抗随剪切位移的变化规律.分析表明,同轴电缆时域反射系统波形尖峰信号幅值随剪切位移增加而增加,不同型号的同轴电缆的剪切位移与阻抗之间基本上成线性关系.

Based upon the application of the time domain reflectometry (TDR) in the monitoring of the defective coaxial cable, a calculation model of TDR system was presented to study the propagation characteristics of electromagnetic wave in defective coaxial cable system. The propagation characteristics of electromagnetic wave in three types of sheared coaxial cables were tested. The influences of coaxial cable's shear deformation on the characteristic impedance of coaxial cable and the TDR signal were analyzed. The theoretical and experimental results show that the ratio of the impedance of a coaxial cable to its shear deformation is almost a constant, which depends on the type of the cable; and that the spike of reflection wave increases with the shear deformation. Therefore, it is applicable to monitor the slope stability by observing the reflection signal of TDR system.