New methods to determine the impedance of UHF RFID chips

This document proposes two new methods which allow the determination of the chip impedance of an UHF RFID chip in different ways. The first method which is similar to existing procedures requires a network analyzer but no additional signal source. The second method is based on the extremely narrow wake up threshold of an RFID chip and the power mismatch between chip and source. By using a set of different and known source impedances also different wake up power signals will result. This allows the accurate calculation of the chip impedance exactly at the wake up threshold. In the simplest form a low cost impedance measurement system could be realized with a standard RFID reader system and few external rf components.