Abstract
The frequency-domain transmission-line equations for parallel planar transmission lines are derived in this paper. Such a general formula is very useful in order to analyze the characteristics of arbitrary transmission lines. And the hypothesis, i.e., the existence of non-zero diagonal parameters in the parameter matrix, made by Haase and Mei is validated through a sound theoretic derivation. The non-zero parameter takes into account the effects of discontinuity, radiation and higher modes of the lines.