Load-pull measurements of differential amplifiers

Microwave systems make more and more use of SiGe devices, which are build with differential connections. Unfortunately, the commercially available measurement systems are mostly developed for single-ended interconnects. For the linear characterization of circuits this is not a restriction. By measurements of all single-ended S-parameters the complete description of the devices is available. But, for large-signal operation such an approach of superposing 2-part measurements is not longer possible. A direct method to determine the properties with simultaneous drive signals at input ports and measuring both output signals in amplitude and phase is required.