DC-Compliant Macromodels Based on the Method of Characteristics for Frequency-Dependent Transmission Lines

This paper investigates a possible source of inaccuracy for transmission line macromodels based on the method of characteristics (MoC). We show that, for the general class of lines with a vanishing DC conductance, the standard procedure of delay extraction followed by a rational function approximation of characteristic admittance and delay less propagation operators may lead to a wrong DC behavior of the macromodel. This degeneracy may be resolved by a suitable perturbation on the DC conductance. We show that this perturbation can be designed in order to ensure arbitrary accuracy of the DC response of the macromodel, without affecting the accuracy and efficiency of the MoC formulation