Experimental plane wave and random field coupling to uniform and non-uniform transmission lines

This paper aims at the investigation of similarities and differences between the coupling mechanisms of an unknown electromagnetic field to a transmission line routed in an unknown way. As opposed to many other studies, this work is focused on the creation of an experimental, simplified, statistical, macro-parameter based model to be used as a quick “rule of the thumb” solution. The measurements have been performed in a GTEM cell and in a reverberation chamber, creating a plane wave and random illumination, with uniform and non-uniform transmission lines. It has been shown that the variation of results of different lines with same macro-parameters, placed in multipath environment becomes lower for higher frequencies, and an asymptotic approach is reasonable. The worst case, i.e. strongest coupling, scenario is extracted and compared for two different field excitation mechanisms. Then, the error is considered when simplifications are made, like approximating a non-uniform line with a straight one, or the threat underestimation if only one cable geometry is measured.