TERAHERTZ ATTENUATION AND DISPERSION CHARACTERISTICS OF COPLANAR TRANSMISSION-LINES

We present experimental verification of analytic formulas for the dispersion and the attenuation of electrical transient signals propagating on coplanar transmission lines. The verification is done in the frequency domain over a teraherz range, although the experiments are in the time domain. The analytic formulas have been obtained from fits to the full-wave analysis results. We quantitatively verify that the full-wave steady-state solutions can be directly applied to the transient time-domain propagation experiments. We use subpicosecond electrical pulses and an external electro-optic sampling technique to obtain the time-domain propagation data. From the Fourier transforms of the time-domain data we extract both the attenuation and the phase information as a function of frequency. The dispersion and the attenuation characteristics are investigated for both coplanar waveguide and coplanar strip transmission lines. The investigation was also carried out on both semi-insulating semiconductor and dielectric substrate materials and indicates no observable losses caused by the semiconductor material.