Temperature sensor based on frequency‐coded chipless RFID tags

Abstract

In this article, the integration of a frequency‐coded radio frequency identification tag with an integrated temperature sensor long lifetime is proposed. It is demonstrated that temperature range can be measured and coded in a tag using tunable stub‐loaded dual‐band resonator that is connected between two orthogonal wideband antennas. The sensor tag emits two different frequencies: the first resonance is used for identification of sensor tag whereas the second frequency is equivalent to temperature. The second resonance is tuned with a varactor controlled by a negative temperature coefficient sensor and its low‐power consumption conditioning circuit. The conditioning circuit modifies the voltage of the varactor and this modifies the second resonant frequency. The resonant structure is studied as a proof of concept. Experimental results at different distances are provided. © 2014 Wiley Periodicals, Inc. Microwave Opt Technol Lett 56:2411–2415, 2014