Modeling the Frequency-Dependent Series Parasitics of Ground–Signal–Ground Pads Used to Probe On-Wafer Microstrip-Line-Fed Devices

This paper presents a model for the parasitic series resistance and inductance of pads used to on-wafer probing of microstrip-line-fed devices. The model accounts for the frequency-dependent current distribution and skin effects, as well as for the geometry of the pad array, which allows to obtain the series parasitics without the need of measuring a “short” dummy structure. Accordingly, these closed-form formulas can be used by designers in order to predict the series parasitic effects introduced by the pads. In this paper, the proposal is used to correct experimental S-parameters from the pad parasitics on inductor and transmission line measurements requiring the implementation of only an “open” dummy structure. Finally, results as good as those corresponding to using experimental data measured on open and short dummies are obtained up to 40 GHz.