In this paper

the propagating modes of the asymmetrically supported broadside-coupled coplanar waveguide are analyzed with the quasi-static method.The correct criteria for C and π mode are given.The mistakes in the presented papers are corrected.The correct and complete formulas of voltage ratios

current ratios on two lines

effective dielectric constants and mode impedance for C and π mode are given.For the structure where dielectric medium in the upper layer is air and the dielectric medium in the lower layer is quartz or duroid

the curves of the effective dielectric constants and mode impedance for C and π mode are presented respectively.These results could be used as references for the analysis and design of this kind of circuits in three-dimensional (multilayer) microwave integrated circuits.