Research On Anti-electromagnetic Interference Technology Of Filter In Trackside Monitoring Equipment

The outdoor monitoring system is a software and hardware platform supporting the operation status monitoring,fault diagnosis and intelligent maintenance of various trackside equipment in rail transit.The data support can be provided for the fault diagnosis of outdoor equipment of track circuit through the information collected by PTX.According to the information collected by PTX,the operating status of outdoor equipment is monitored in real time,reducing the trouble of manual periodic inspection and repairing.When outdoor equipment fails,it can promptly report to the police and provide location and repair suggestions for the faulty area,which can shorten the repair time.The power carrier communication cable is laid on the trackside for a long time,which is easy to be interfered by the high-order harmonic of trackside traction current and high frequency transmission signal of transponder.It prevents electromagnetic interference generated by power module from entering the transmission channel to interfere with the high frequency signal of power carrier,while the input end of broadband power carrier signal is high-frequency interference noise to the input end of filter circuit,so that the energy value to power carrier module is very low,which will directly affect the transmission distance,thus causing packet loss.The specific work content of the thesis is as follows:Firstly,the difference between the tuning matching unit(PT)and the PTX,and the electromagnetic interference caused by the PTX in the process of information transmission is introduced in this thesis.The design theory of the filter circuit such as differential mode interference,common mode interference,insertion loss,impedance mismatch principle is analyzed in detail on the basis of mastering the characteristics of electromagnetic interference in the transmission process.Secondly,the simulation software is used to reproduce the existing filter problems according to the above related theoretical knowledge.The filter circuit is optimized to solve the existing problems,by appropriately increase the number of stages and change the value of the components.Then a filter circuit is designed by replacing the common mode inductor with the transformer model because of the similar between the model for transformer and the inductor in the simulation software.The simulation results show that the protection of the filter circuit of the transformer model to the broadband power carrier signal is slightly improved,and the protection of the improved version of the filter circuit is greatly improved.Finally,the time domain waveform of broadband power carrier signal is tested,and the spectrum is obtained according to the Fourier transform in this thesis due to the acquisition extension in PTX is designed with the power carrier communication module as the core.The three filter circuit diagrams designed in this thesis are made and the performance indexes such as insertion loss are tested.The experimental results show that the sensitivity of carrier receiving with optimized filter is improved.