Simple RC models of distributed RC lines in consideration with the delay time

Two simple lumped RC circuits are presented to model a single distributed RC line by very simple passive RC two-port network. These circuits give very accurate results for the 50% propagation delay of the RC distributed lines terminated with arbitrary load impedances. We first show that the step responses for the open circuited voltage transfer function, short circuited transfer admittance function, and the short circuit current transfer function which can be approximated accurately by functions of degree one or two as far as we concern with the delay characteristics.