A Hybrid Time/Frequency Domain Near-Field Chipless-RFID system
Amirhossein Karami‐Horestani, Ferran Paredes, Ferran Martı́n
Abstract
A novel encoding strategy for near-field chipless-RFID systems based on sequential bit reading is proposed in this paper. The tags consist in a chain of C-shaped resonators (inclusions) etched (or printed) at predefined positions in the tag substrate. However, contrary to previous near-field chipless-RFID systems, encoding is not achieved by the presence or absence of functional inclusion at their positions, but through the dimensions of the inclusions. Thus, the C-shaped resonators can exhibit four different dimensions in the direction transverse to the chain axis, corresponding to four different states, or two bits, per inclusion. By this means, the number of bits of the whole system is twice the number of bits of the tags based on absence/presence of functional inclusions. For tag reading, the chain should be displaced at short distance on top of the reader, a transmission line with a gap feed by four harmonic signals tuned to the resonance frequencies of the four different C-shaped inclusions. Thus, in this system, the data is encoded in frequency, but the bits are read sequentially, by means of a time-division multiplexing scheme. This justifies the designation of this novel approach as hybrid time/frequency domain chipless-RFID. The paper reports a first proof-of-concept demonstrator, where the tags are based on four inclusions, providing 8 bits.