Novel Compact Flexible Chipless RFID Tags

Two novel, compact, U-shaped slot resonator-based 8-bit chipless RFID tags covering wide-band for identification, tracking and sensing applications are presented in this paper. The tags are designed on a flexible DuPont substrate having relative permittivity 4, loss tangent 0.027 and thickness 50 mu m. Both the tags have the same structure, but are arranged differently. In tag-1, 8 U-shaped resonators are arranged in a cascaded fashion, whereas in tag-2, one set formed by alternate 4 slots are arranged in one half of the substrate, while the remaining are arranged in the second half with an inverted configuration. The Radar Cross Section (RCS) responses of the two tags are obtained to demonstrate the 8 unique resonances with adequate separation. A flexibility study has been carried out to validate the distinguishable nature of bits under different bending conditions. An experimental set up with two wide-band antennas are used to measure the S-21 of the fabricated tags in the laboratory. Different arrangements of antennas to establish the reflected and transmitted signal performance of the proposed tags are presented in this paper.