Attenuation characteristics of coplanar waveguides at subterahertz frequencies

We present experimental and simulation data of subterahertz attenuation of coplanar waveguides (CPWs) with wide and narrow ground planes. Experimental data are obtained by using a subpicosecond measurement technique based on electrooptic sampling. While time-domain data qualitatively describe the attenuation characteristics, they are converted to the frequency domain by a Fourier transform to give a quantitative interpretation. Simulation data are obtained by full-wave analysis and compared with the experimental results. It is shown that the simulation results consistently agree with experimental results. Furthermore, in the case of CPWs with wide ground planes, both of them are consistent with analytical theory. While CPWs with narrow ground planes have not been analytically studied, our results show that they suffer considerably lower attenuation, which we attribute to a reduced coupling between the CPW mode and substrate modes. The effects of ground-plane width and line dimensions on the attenuation characteristics are discussed in detail.