Enhanced transmission line theory: Frequency-dependent line parameters and their insertion in a classical transmission line equation solver

In this paper, a modified enhanced transmissionline theory taking into account higher-order modes is described. The new equations are based on the correction of the per-unit-length parameters that become frequency dependent and contain the radiation resistance. In particular, the per-unit-length resistance takes into account this radiation resistance and an additional resistance proportional to the imaginary part of the characteristic impedance. This additional resistance is identified as responsible of the current attenuation on the line. These new parameters are described in a per-unit-length RLCG form and can then easily be introduced in a classical transmission-line equation solver. Satisfactory results are obtained when comparing this new model to a full-wave model.