High Encoding Capacity Chipless RFID Tag

In this work, we introduce a novel chipless RFID tag with high encoding capacity, which uses sub-band frequency shift coding (SB-FSC) to increase the number of bits encoded by each resonator. The tag consists of an array of N variable-length microstrip line resonators, each with up to M = 9 notches (corresponding to digits 0-9) to encode N x log2M bits/tag. In addition, a pair of microstrip resonators serves as a frequency reference. A 60 x 80 mm2 proof-of-concept tag is demonstrated with 13 + 2 resonant microstrip elements (for GTIN-13 code) to provide 43 bits/tag. The tag operates in the frequency range from 1.4 to 4.2 GHz with a coding density 36.7 bits/lambda(2)/GHz at the center frequency. The presented design thus enables the integration of chipless RFID technology with the GS1 standard systems and Internet of Things (IoT) paradigm.