A New Nested Concentric Stepped Impedance Resonator Structure for the Implementation of High Capacity Chipless RFID Tags

In this paper, a new stepped impedance resonator (SIR) based chipless RFID tag is introduced for the implementation of compact tags with high spectral efficiency. The proposed tag provides a 12-bits encoded data within a physical dimension of $(19\times 14.5)\ mm^{2}$ . Thereby, our tag design provides a bit density of 4.5 bit/cm2. Each encoded data sequence is represented as a unique spectral selection in the frequency domain within the frequency band from 5.4 GHz to 13.7 GHz. The resonator components are arranged as two typical sets of nested concentric loops. The proposed peculiar geometry and resonant element orientation would reduce the inter-resonator coupling, allowing higher bit density as well as stable oblique angular output to be achieved. The multi resonators are fabricated on a lossy FR4 substrate having a dielectric constant $\varepsilon_{r}=4.3$ , loss tangent $\delta=0.025$ , and $h= 1.6\ mm$ . The measurement results and simulations of the radar cross section (RCS) response of the tag are highly matched.