Analysis Of Anti-interference Performance And Relevant Circuits Technology Of The Railway Disaster Monitoring System Based On BeiDou Satellite Communications

Safety is eternally a most-concerned topic of the railway system. In China, the railway lines are widely distributed. And since of the complex terrain, different types of natural disasters occur frequently in our country. In recent years, the disasters have caused serious destructions for the railway, not to mention the potential disasters that may also seriously threaten the safety of railway operation. Therefore, a disaster prevention and monitoring system along the railway line should be established to detect these natural disasters and emergencies.The object of study in this paper is the disaster prevention and monitoring system that mentioned above, which is based on the communication by BeiDou satellite. Two main invasion ways of electromagnetic interference into this system are proposed as follows. One is that the spatial electromagnetic interference will be introduced into the communication link through the wireless channel of the BeiDou satellite communication system. The other one is the common-mode induction ways. By these ways, the ambient electromagnetic disturbance in the railway environment may be introduced into the sensitive circuits, and that will give a strong impact on the system. Therefore, the following part of this paper will commence around the two aspects.The first topic of this study is the evaluation on the anti-interference performance of the BeiDou communication system, against various electromagnetic noises in the wireless channel. In order to analyze the relation between the spreading gain and the anti-interference capability, modeling and simulations of a typical direct spreading spectrum communication system were introduced. By the comparison of performance under different electromagnetic conditions, it comes to the conclusion that even under harsh noisy channel the reliability of the BeiDou system is still pretty good.And then, the research on the anti-interference performance of sensor circuits which is used to collect the information of disasters was carried out. Through analyzing the CMRR of amplifier with different circuit structures, it shows that the differential amplifier circuit and the three op-amp measuring circuit have better performances. Furthermore, the CMRR of the amplifier can be improved to above80dB with the "driven shield" technique, thus the interference of weak signal processing circuit can be reduced on a great deal.