Sensing of thermal thresholds using UWB RFID passive tags

In this work a wireless temperature sensor is developed to detect thermal thresholds. It consists of a completely-passive ultra-wideband radiofrequency identification tag, based on an antenna connected to a delay line. The delay line is loaded by a nitinol thermal switch. The switch modifies the amplitude of the backscattered signal when a temperature threshold is surpassed. The sensor is able to store the occurrence of the thermal threshold violation and performs the sensing activity independently of the reader interrogation. The length of the delay line defines a unique identification code for the sensor, which is read using a low-cost ultra-wideband radar.