Electro-Magnetic Compatibility Design for Rapid Transit Systems

Design criteria and techniques used to minimize the interference levels between the communication and signal channels for control of rapid transit vehicles and other working systems (such as propulsion, power system, auxiliaries, etc.) or the environment, are analyzed in this paper. The particular system under consideration utilizes a higher frequency band to allow a wide separation from signal to noise, but below 10 KHz and at low power level so that it does not require special license to operate. In addition, the use of Frequency Shift Keying (FSK) and the well known features of signal capture as developed in F.M. Systems are used to further increase the Electro-magnetic Compatibility (EMC) of the overall system. The automatic train control (ATC) engineer must always design his equipment to interface with the outside world, but under some circumstances he may be able to influence the design of other subsystems to meet his particular requirements. For that reason it is extremely important that the ATC and propulsion or power engineers work hand in hand to achieve the electro-magnetic compatibility required in today's systems. An example of such activity is presented to illustrate the extreme importance of designing a transportation system as an integral part of its environment, versus the design of individual subsystems which do not have well defined interfaces. The techniques presented in this paper have been successfully implemented in various transit systems which are presently in operation.