UHF RFID Sensor System Using Tag Signal Patterns: Prototype System

This letter presents a novel passive radio frequency identification (RFID) sensor prototype system in the ultrahigh frequency (UHF) range, which is based on the detection of fully controlled patterns of the backscattered transponder (tag) signals. The UHF RFID tag antenna itself is used as the sensing device. A custom-built sensor tag has been designed to monitor the water filling level of a canister (i.e., canister full or empty). The measurement results of the prototype system compare well with electromagnetic simulations and verify the novel sensor system concept. As predicted by the model, the prototype system solves the two main issues in antenna-based RFID sensor systems experienced so far, i.e., the impairment of system performance by modulating the sensor state information on the tag signal and the need for recurring system calibration due to changes in reader-tag distance.