Frequency-dependent characteristic impedances of a broadside-coupled coplanar waveguide

The frequency dependent characteristic impedances for the even and odd modes of the broadside-coupled coplanar waveguide (CPW) are calculated using the spectral domain method. Numerical results as a function of frequency for the various structure parameters are presented and discussed. From these results, we can know that the dispersion effects of characteristic impedances are larger than those of effective dielectric constants in broadside-coupled CPW, so design parameters which are considered frequency-dependent factors must be required for high-frequency circuit design such as MMIC application. The results of this paper will be useful for design and fabrication using the broadside-coupled CPW.