Nano-scale devices and high power transistorsudpresent extreme impedances, which are far removed from theud50-Ω reference impedance of conventional test equipment,udresulting in a reduction in the measurement sensitivity asudcompared with impedances close to the reference impedance. Thisudletter describes a novel method based on active interferometryudto increase the measurement sensitivity of a VNA for measuringudsuch extreme impedances, using only a single coupler. Theudtheory of the method is explained with supporting simulation.udAn interferometry-based method is demonstrated for theudfirst time with on-wafer measurements, resulting in anudimproved measurement sensitivity for extreme impedance deviceudcharacterization of up to 9%.
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