High coding capacity chipless radiofrequency identification tags

A novel tristate coupled line microstrip resonator is proposed for compact chipless radiofrequency identification tags. The proposed resonator can be reconfigured to present one of the three possible states: 00, 10, and 01, which denote no resonance, resonance at f₁, and resonance at f₂, respectively. The resonator can be designed with f₁ and f₂ at appropriate positions, reducing the required spectrum. A multiresonator prototype consisting of 14 elements of the proposed resonator is designed, analyzed, and experimentally characterized. This prototype is implemented on an RT Duroid 5880 substrate with a dielectric constant of 2.2 and a thickness of 0.78 mm. The prototype can be reconfigured for 3¹⁴ codes. A test-bench comprising six resonators and transmitting and receiving wideband antennas is established and used to experimentally characterize a prototype tag. The experimental results exhibit good agreement with the simulation.