The Research On Balise Signal Affected By Pulsed Current

Balise is a location verification device for the train control system, which is working with Balise Transmission Module (BTM) on the train. The relevant information is transmitted to Automatic Train Protection (ATP) for ensuring the train traffic safety. However, the "Lost Point" and "Ghost Balise" phenomena are affecting train traffic safety.Firstly, Balise antenna coupling model in the communication was built from the electromagnetic theory and the characteristics of Balise system. Signals coupling process in communication interface was analyzed in field-coup ling way and then coupling in the dynamic condition was discussed. By adjusting the vertical height and the BTM receive threshold appropriately can enhance the reliability of the system, what’s more, multi-storage units can avoid side-lobe interference.Then the Balise communication was analyzed and introduced. Common non-coherent demodulation methods are optimized to adapt to the Balise communication system. Because of the characteristics of FSK, communication system cannot be immune to high amplitude pulse interference in the BTM passband. The encoding and decoding method of Balise can effectively guarantee the telegram security during transmission, therefore, interference mainly makes the normal error bit or generates the unrecognized telegram to cause the system error. According to the relevant standards, the spectral distribution of pulsed interference is analyzed, moreover, strong energy distribution of Electrical Fast Transient and Electrostatic Discharge within4-6MHz can affect the communication.Finally, the interference mechanism was discussed. Pulse current is generated by the running train and the response in the BTM reception band is a focus. The statistical characteristic of the pulse current was described with a large number of measured data. Based on the statistics similarity of measured pulse data and the BTM antenna port, the actual size of interference coupling model was established, thus the differential mode amplitude in BTM antenna port generated by pulse current can be calculated. By comparing the differential mode voltage with the voltage converted from common mode current on the antenna cable, the result demonstrated that differential mode coupling is the main coupling path. To further illustrate the existence of the current pulse interference on the Balise communication, interference was added to signal demodulation process to simulate error bit position.