Full-wave analysis of coplanar waveguide and slotline using the time-domain finite-difference method

The authors present a detailed full-wave analysis of a coplanar waveguide (CPW) and a slotline by the time-domain finite-difference (TD-FD) method. The transient waveforms propagating along the coplanar waveguide and slotline, which are excited by retarded Gaussian pulses, are found in the time domain. After the time-domain field distributions are obtained, frequency-domain parameters such as the effective dielectric constant and the complex characteristic impedance are calculated using Fourier transformations. The results agree well with available theoretical and experimental data over a wide frequency range. The validity of the quasi-TEM assumptions for CPW and slotline analyses is also checked by evaluating the ratios of the longitudinal and transverse field components directly