Effect of impedance control on the response of aircraft cable to external electromagnetic fields

Recent industry measurements indicate that the protection of avionics systems in commercial aircraft is provided not by the fuselage but rather by the transmission lines formed between the wires and the aluminum skin. The authors investigate the effects on induced voltage at conditions of unmatched impedances, which are typical of aircraft control systems. A computer program was written to display the variation of induced voltage across the load resistor. This program made it possible to vary the source and load impedances while scanning the response across a broad frequency range. Design considerations following from the calculations are presented. It is concluded that fine structure above resonance calls into question techniques and standards used in radiated susceptibility testing