On the qualification of airborne equipment for radiated emissions

This work deals with the qualification of airborne equipment with regard to unintentional radiated emissions, which can couple into the antennas of navigation and communication systems of aircraft. Extensive transfer path measurements form the basis of this work; emphasis is laid on the statistical analysis of measurement data. Qualification is tackled on two fronts. Firstly, a new EMC test procedure is developed to detect potentially interfering emissions from flight test instrumentation on board. It makes use of detection antennas to measure the electromagnetic environment inside the aircraft. The substantiation of the method employs the concept of subtracted transfer path firstly introduced in this work. Secondly, the reduction of the coupling to aircraft antennas is evaluated after covering the aircraft interior with electromagnetic absorbing films. Results show the importance of wave scattering, the leakage of energy through aircraft doors and windows as well as a modest reduction of coupling to aircraft antennas with absorbing material added to the insulation of aircraft with metallic fuselage. © 2014 Deutschen Forschungsanstalt für Luft-und Raumfahrt. All rights reserved.