Real-time monitoring method of cable coupling signal

Cable coupling is one of the most important reasons for electromagnetic compatibility problems in avionics systems. Monitoring the cable coupling effect is of great significance. A method of monitoring the coupling signals on the ports with the spare wire in the cable is introduced. Since the monitoring wire is in the same conditions as the monitored one, the influence of the stochastic routing and field distribution could be counteracted. The monitoring and monitored wires could be regarded as the same two-port system, which could be described with an ABCD matrix. Then the frequency-domain analytical model of this system could be constructed with the transmission line theory. Finally, it could be converted to a discrete-time model and the signal flow graphs of the system could be achieved, which is convenient for the real-time signal processing and hardware realization. A four-wire cable system is taken as the case to validate the method. Compared with the results of measurement, the errors of the current peaks are less than 6%, which is small enough for practical applications. This fact proves that the method is effective and accurate.