Temporally resolved impedance measurement of differential, RF-powered devices using the example of a microwave rfid front-end

This work was motivated by the idea to monitor the input impedance of differential front-ends of passive RFID-transponders depending on their power-consumption. Different methods readily available in state-of-the-art network analyzers are compared with regard to the special demands imposed by passive RFID front-ends. At this the correct stimulation of the DUT appears to be the major issue of conventional methods. Hereupon a new approach is proposed which for the first time combines the proper stimulation of differential, RF-powered devices with the data aquisition of differential mixed-mode S-parameters in temporal resolution. The new measurement method is applied to a 2.45GHz RFID transponder showing detailed mixed-mode results of its power-up behavior.