Evaluation and reduction of calibration residual uncertainty in load-pull measurements at millimeter-wave frequencies

In this paper, a thorough evaluation of calibration residual uncertainty of on-wafer load-pull systems at millimeterwave frequencies, with actual comparisons between real-time and non-real-time load-pull systems, is reported for the first time. Two figures of merit for uncertainty evaluation are taken into account, showing the differences between the two methodologies. In the case of non-real-time systems, based on a simulation tool developed for the purpose, typical values of uncertainties to be expected at millimeter-wave frequencies are shown. Finally, a methodology to reduce calibration residual uncertainty of nonreal- time load-pull measurements, based on the optimization of a thru load-pull map, is for the first time introduced, and its effects on actual measurements of microwave HBTs at 40 GHz are shown.