Multi-Chip RFID antenna integrating shape-memory alloys for detection of thermal thresholds

Low-cost wireless measurement of objects’ tempera- ture is one of the greatest expectation of radiofrequency identi- fication technology for the so many applications in cold supply- chain control and safety assessment in general. In this context, the paper proposes a dual-chip UHF tag embedding shape memory al- loys (SMA) able to transform the variation of the tagged item’s temperature into a permanent change of antenna radiation fea- tures. This event-driven antenna is hence able to selectively activate the embedded microchips according to the temperature above or below a given threshold. A general design methodology for the re- sulting two-ports tag antenna is here introduced and then applied to prototypes able to work at low (around 0°C ) and high (80°C ) temperatures.