Near-Field Hybrid (Time/Frequency Domain) Chipless-RFID System based on Linear Strips Tag

In this paper, a novel structure to be used in near-field chipless RFID systems based on sequentially reading of frequency coded inclusions is presented. In the proposed system, the reader consists of a transmission line with a gap and the tag consists of a chain of line (strip) resonators. By moving the tag on top of the reader with a small airgap between them, significant transmission in the reader occurs when the line resonator lies on top of the transmission line´s gap, provided the feeding signal is tuned to the frequency of that resonator. The tag is designed by considering four different lengths for the strip resonators, corresponding to four different frequencies, which can be found in the reader´s output according to the length of the line resonator on top of the reader in every time sequence. Therefore, in every time sequence four different states (two bits) can be coded. As a result, the number of bits per length of the tag in this system is twice the number of bits in the tags based on the absence/presence of functional inclusions. According to the explanations above, the reader, which consists of a transmission line with a gap, is fed with four different harmonic signals with frequencies equal to the resonance frequencies of the strip resonators. In this paper, the results related to a tag including four line resonators are provided as a first proof-of-concept demonstrator.