RFID tag antenna based temperature sensing in the frequency domain

The efficiency of cold supply chain operations can be improved with pervasive temperature sensing. In this paper, we investigate the design of a low-cost, single-use RFID based temperature threshold sensor that is capable of relating the violation of a temperature threshold to a shift in the optimal operating frequency at which the tag antenna is well matched to the tag IC. This shift is detectable by commercial UHF RFID readers operating in the 902-928 MHz frequency band. We will illustrate how state change information is preserved using a nonelectric memory mechanism that works even in the absence of reader transmitted power. We demonstrate that the sensor works reliably for a read distance of over 3 m and in noisy environments.