Some limiting aspects of transmission line theory and possible improvements

Abstract

Wiring still supports most of electric power fluxes as well as data transmission in various infrastructures and transport systems. Hopefully, transmission line theory is a very helpful approximation to estimate interference propagation among cable harnesses. This is definitely a useful tool for engineers, since it enables anticipating the probability of failure of equipment they are connected to. Everything has been written from the initial roots of transmission line derivation, dated from the ancient telegraphist's equations established by O. Heaviside back to...1880! until the last developments of sophisticated and off-the-shelf transmission line solvers for complex arrangements of cable networks. The fact is, that these tools are so familiar to many EMC engineers that it might come with some misunderstanding of some results. In this paper, we take a look at the root assumptions of this approximate theory and examine some of its potential weaknesses, through simple examples. Then, we investigate the question of the possible improvement of the classical transmission line theory (when and if required). In principle, this would require the derivation of some kind of generalized transmission line theory or even the examination of the super theory of transmission lines. We rather show that a much more simple modification of transmission line equations is possible for a better approximation of the experimental observations.