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 ¿) line. We measured CPW step discontinuities over the complete range of dimensions permitted by our design rules, and obtained ¿eff for the corresponding range of line impedances (23 ¿ to 94 ¿ 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.