Ultra-wideband slotline dispersion measurements using ring resonator

The design for an ultra-wideband coplanar waveguide-fed slotline ring resonator is presented. The broadband feed system permits dispersion measurements to be made over the frequency range 2?220 GHz using a single circuit and coplanar waveguide probes connected to a vector network analyser. Measured effective dielectric constant data from a number of different rings using thin-film copper on alumina is presented, and compared with a theoretical prediction using the spectral domain approach, the agreement being better than 3.5%.