RFID Multiprobe Impedance-Based Sensors

In this paper, a passive multiprobe sensor using conventional UHF radio frequency identification (RFID) tags is presented. The RFID link between the reader and the tag is analyzed from a general point of view by means of reciprocity principle, to obtain a compact and explicit expression of the response of RFID tags that can be exploited in sensing measurements. A calibration scheme to remove nonlinearities in the response of RFID tags, which are due to the scavenging powering mechanism of passive tags, is also presented along with measurements. Finally, experimental results and discussion of a complete multiprobe sensing scenario are used to show the different challenges involved and how to overcome them.