Realisation of a High Spectral Efficient Chipless RFID Tag using Hairpin Resonators

Recently, chipless radio frequency systems have significant development and are going to be commercialised in the near future. Due to the planar structure of the chipless tags, this technology has a high potential for sensing and identification with a low price compared to that of the chipped RFID. However, lower data capacity is one of the crucial challenges for frequency domain chipless RFID tags due to limited available bandwidth resources and the quality factor of the resonators. On the other hand, the implementation of low-quality factor resonators design in the printed tag is not feasible due to broadening the resonances. Therefore, designing high-quality-factor resonators for chipless RFID tags is a need. In this paper, a high spectral efficient hairpin resonator for chipless RFID sensing and identification is proposed. To demonstrate the design concept, using the proposed resonators, a 40-bit chipless RFID tag with 3.5 GHz operating bandwidth was designed, fabricated and measured. This design has the potential to arrange 50 resonators in less than 4 GHz bandwidth.