Information Fusion Based Temperature Sensing With Passive UHF RFID Tags

Ultra High Frequency Radio Identification (UHF RFID) technology has been widely used in logistics and chain management. Many methods exist to implement temperature sensing on passive RFID tags, such as utilizing high-cost RFID chips with temperature sensors. The resistance of a semiconductor diode in an RFID chip is temperature-sensitive, and then the discharging time through the reverse-polarized diode could be used to estimate temperature indirectly with the competitive advantage of being low-cost. However, the discharging time is inaccessible in the RFID standard Gen2 protocol, while the persistent time consisting of the discharging time and the charging time is accessible. In this paper, differential data of the persistent time and the charging time is defined, and a mapping model between temperature and differential data is built. An optimal fusion factor is determined by minimizing the regression error of the mapping model under various radiated power levels. This process eliminates the influences of measurement setups, such as relative distance and orientation between the read/write device (RWD) and tags, on the discharging time. Compared to existing methods, proposed method improves the sensing accuracy from ±5°C to ±2°C under different measurement setups.