Time-coded chipless RFID tags: Design, characterization and application

This paper deals with time-coded chipless RFID tags. These tags consist of an ultra-wideband scattering antenna connected to a delay line. The paper introduces their basic theory of operation, explaining the behaviour of the two scattering modes (structural and tag modes). The tags are measured using a low-cost time-domain impulse-radio ultra-wideband radar which takes the role of the RFID reader. The tags are characterized in terms of tag-to-structural modes ratio, read range, tag-reader angle and the impact on the tags´ performance when they are attached to materials. Finally, the potential of time-coded chipless tags to implement completely-passive wireless sensors is addressed and future applications are proposed.