Train Axle Detector Based on Signal Codification with a Barker code 2001-01-3257
This paper presents the development and implementation of an electronic axle detection system applied to trains passing a predetermined point on a railway. The system permits detection even if the train is travelling at a velocity of up to 350 Km/h, depending on the diameter of the train wheel. The system uses two coils placed on either side of the rail, one used as an emitter and the other as a receiver, which, as a result of the attenuation of the electromagnetic field between the coils, detect the passing of the train wheel. In contrast to other systems with similar characteristics, in this case the signal emitted is specially coded (using a 13-bit Barker code). On reception, a correlation algorithm (implemented in an FPGA) enables the signal emitted to be detected even if there is a low signal-to-noise ratio. By using this technique, the system is also able to reject a great deal of interference coming from electric motors or other electromagnetic sources. Furthermore, a slight variation of the frequency of modulation of the signal emitted allows two systems to be used with no interference between them; useful when the direction of travel has to be determined.