Nonuniqueness of modal transformations for multiconductor transmission line problems

This research paper aims at showing that in the context of frequency-domain multiconductor transmission line problems, it is pointless to look for uniquely defined modal transformation matrices and, as a corollary, to assign any physical meaning to the modal characteristic impedances. Several nonunique ways for defining the modal transformations are presented and discussed. With this contribution, we hope to be able to prevent researchers from spending their time pursuing an impossible quest.