High-RCS Wide-Angle Retroreflective Tags Towards THz

Double-Notch Frequency-Coded Corner Reflectors for sub-THz Chipless RFID Tags

“…First, the two tags that operate in the upper part of the sub-THz spectrum (220 GHz to 330 GHz) employ FSSs, due to their simplified manufacturing complexity. Second, the tag presented in this work can implement up to 15 signatures within the WR-3 band, trice as much as the previous state-of-the-art [16] at this frequency range, and of the order of / greater than other W-band works, which feature either two notches [11] or photonic crystal cavities with narrower resonance bandwidths [13]. Third, one drawback of the approach presented in this work is the aforementioned 1.5 dB loss in σ tag , compared to the CR.…”

“…The other publications showcased in Tab. II do not present this issue, owing to either coding only one f res in the FSS [14], [16] or using dielectric resonators with narrow resonance bandwidths [11]- [13].…”

“…The aforementioned tags operate within the W-band (75 GHz to 110 GHz), with tags based on dielectric resonator arrays and FSSs having been recently verified as a part of an indoor synthetic aperture radar system , achieving positioning accuracy in the millimeter range [15]. However, only FSSs have been demonstrated up to the upper sub-THz range (WR-3, from 220 GHz to 330 GHz), due to their easiness of fabrication via lithography-based processes [16], whereas the other structures still present significant challenges in terms of manufacturing complexity at this frequency band. Further, the work in [16] features only one notch with a 20 GHz bandwidth in the tag's frequency response, which restricts the number of codes implementable within the WR-3 band to 5, limiting the suitability of such tags in a real indoor environment, where a minimum of 10 tags are needed for accurate 3D localization [12].…”