The Research Of Crosstalk Between Shielded Cables Of Electrical Multiple Units

The arrangement of cables of equipments on the EMUs is a key factor of electromagnetic compatibility (EMC) for systems. A lot of electronic equipments and cable wiring harness are placed together in the carriage where strong and weak signals are intertwined, which causes varying degrees of coupling between cables. Improper arrangement will cause electromagnetic interference. Crosstalk between cables on EMUs and immunity measures were analyzed thoroughly in this thesis based on the transmission line theory.Firstly, for lower and higher frequency band, lumped-parameter model and distributed parameter model were used respectively to analyze the crosstalk between cables. In the lumped-parameter model, both the electric coupling and magnetic coupling were considered. The effect of grounding on crosstalk was obtained through the in-depth analysis of the shielding layer function. By analyzing the distributed parameter model based on the transmission line theory and the two-port network theory, the calculation method of crosstalk current was obtained, and the method of distributed inductance and distributed capacitance between cables was derived as well.Based on the above theory, crosstalk current was taken as a study object in this thesis due to the fact that the current is easier to be obtained than voltage, and a simulation model was established which was more suitable for the research of crosstalk between cables on the EMUs. A series of operations were simulated in MATLAB and the effect on crosstalk of spacing, height and different earthing patterns was obtained in quantitative analysis. To optimize the simulation model, the pigtail was taken into account in the model, in which the relationship between crosstalk and the length of the pigtail, the spacing between pigtail and core wire and the length of the exposed cable core wire was analyzed in detail.A test platform was set up based on the above simulation model. The method of RF induction was used to generate the interfering signal in the interference cable while the disturbed cable was unshielded or shielded cable. The effect of different parameters on crosstalk was tested in frequency domain. The experiment data agreed well with the simulation data, which verified the validity of the theoretical model. Concrete measures to reduce the crosstalk were proposed based on the results of the simulation and the tests. In addition, a simulation software with a friendly interface was wrote, in order that the curve of crosstalk between cables could be obtained easily and intuitively by the non-professionals.