Development of a spread spectrum transmission system for track circuit

The Japanese high speed train-Shinkansen-has had in its 30 years history, no fatal accidents. Its safety is secured by the signalling system, which is called ATC-automatic train control. The principle of this ATC system is that the speed signal information is transmitted to the rolling stock from the rail track. The rail constitutes a rail track distributed transmission line, and the transmission mode is single side band which is synchronized by the power supply. Since Shinkansen is electrified by AC 60 Hz 25000 V, this system can avoid its harmonic waves effectively. Nevertheless the electromagnetic environment of Shinkansen has worsened. The reason is the introduction of high power rolling stock. The high power rolling stock realize 270 km/h operation, and since this high power rolling stock uses VVVF system-variable voltage and variable frequency-the harmonic waves are not so simple. To endure such an environment we have succeeded in experimenting with the spread spectrum transmission system at the rail track, and report this here.