Abstract
In Japan, automatic train control (ATC) systems, one type of railway signaling system, transmit train control information by using analog signals based on amplitude modulation (AM) in the audio frequency band. To realize highly functional train control by increasing the data transmission speed, there have been many studies on digital ATC that transmits train control information by using digital signals based on phase shift keying (PSK), and these systems are employed in some railway lines. In practice, however, it is difficult to install digital ATC because it is impossible to ensure another transmission band for digital ATC signals due to the existing track circuit configuration and interoperability conditions, and there are many railway lines in which analog ATC is still employed. To overcome this restriction, we proposed a novel railway signaling system using mixed digital and analog signals. We employed quadrature PSK (QPSK) for digital signals and developed a transmission device using digital signal processors. We evaluated the transmission characteristics by conducting a basic experiment. In addition, it is important to improve the performance of digital ATC systems after they were completely shifted by using mixed digital and analog signals. Therefore, we also studied a performance improvement method by applying quadrature amplitude modulation (QAM) and code division multiple access (CDMA) in which the increase of data transmission speed is realized.
