Time- and frequency-domain coupling analysis of field-to-nonuniform transmission lines

The coupling of an external electromagnetic wave to a nonuniform transmission line (TL) of finite-length suspended above a conducting ground plane is considered. The externally excited nonuniform TL is approximated by a cascaded series of uniform TLs together with a suitable set of equivalent distributed voltage and current sources along the line to account for the effect of the external source. A few typical line geometries, relevant in the EMC field, are studied to confirm the validity of this method. Comparison of this approach with the rigorous MoM solution and laboratory experiments indicates that this simple circuit-theory-based method provides reliable results.