Chipless RFID tags for passive wireless sensor grids

This paper discusses the potential of some chipless RFID tags in term of sensing. Two configurations of chipless sensor tags are studied and experimented. The first configuration is based on a chipless RFID tag coded in frequency domain and transformed into a sensor thanks to a deposit of a nanomaterial that exhibits high sensitivity to humidity. One of the advantages of such a transformation is to combine both identification and sensing in the same and unique device. Very interesting sensitivity is observed in practice. The second configuration is based on the use of frequency coded tag where sensing capability consists in measuring a flight time. Then several sensors located on an object in preselected positions are used in order to monitor the deformation of the object. Interesting accuracy better than 500 μm is observed in practice. It is demonstrated that anti-collision schemes can be implemented leading to read concurrently several chipless sensor tags.