, we can now introduce a model to study the effect of signal radiation and mode conversion on a generic PLN. First, we rely on the MTL theory to describe the propagation of CM and DM signals along each power line cable. The relations between signals at the two edges of a cable is then described using a mixed-mode scattering matrix (MMSM). MMSMs are also used to characterize all the other devices and loads present in a PLN. By converting the MMSMs to transmission matrices (MMTMs), it is then possible to use the chain rule and represent the whole PLN connecting any two network nodes by a single equivalent MMTM, from which the modal transfer functions can be computed. We point out that scattering and transmission matrices are here only used for convenience, since high-frequency characterization is usually performed with vector network analyzers that measure scattering parameters. The entire network can be equivalently represented in terms of voltages and currents. The fundamental concept is here to use a mixed-mode representation in order to characterize both DM and CM.

In the following, we summarize the theory about scattering matrices, MMSMs and MMTMs and the conversion equations between each representation.

Three-conductor and 