On-Wafer Characterization of CPW Step Discontinuities by a One-Port Method

We have introduced a useful one-port method for characterizing a certain class of transmission line discontinuities. We have used it to characterize CPW steps and to obtain the susceptance of a circular aperture in a WR-28 waveguide. In the former case, the method yields the normalized discontinuity admittance and the propagation constant of the line that creates the discontinuity with a reference (
⁵⁰
Ω) line. We measured CPW step discontinuities over the complete range of dimensions permitted by our design rules, and obtained ϵeff for the corresponding range of line impedances (23 Ω to 94 Ω approximately). Although Fig. 2 might suggest that the characteristic impedance of the CPW line is dispersionless, it should be noted that the presented impedance is normalized to a reference CPW line that is dispersive.