Compact Multi-Band Chipless RFID Resonators for Identification and Authentication Applications

Moving towards commercialisation of chipless RFID systems, there are still some pressing issues. In the tag design level, the issues are high data capacity in the order of tens of bits, compact design and the immunity to the interference which can be achieved by a cross-polar response. It is demanded to yield the highest numbers of bits in a tag ID while the occupied physical space and allocated bandwidth are minimised. Increasing the number of resonators in a conventional multi-resonator chipless tag causes a significant tag size growth. The destructive coupling effect between resonators in multi-resonator tags is another critical issue. In this Letter, to combat those issues, a multi-band resonator is proposed. The comb-shaped tags contain both co-polar and cross-polar Radar cross section (RCS) responses, hence they can be used in high reflective environments. Two samples of 14-bit and 40-bit comb-shaped tags are designed, which have physical sizes of 17 mm × 13 and 30 mm × 45 mm, respectively. The promising performance of the proposed structure, which is beyond the state of art hybrid and frequency-domain tags, shows the potential of the proposed designs for identification and authentication applications.