Ultrathin and Bendable mm-Wave Chipless Tags Based on Grounded Periodic Surfaces

Depolarizing mm-wave chipless radio frequency identification (RFID) tags based on grounded dipole resonators characterized by an extremely thin profile are proposed. The use of a thin grounded substrate (below 0.15 mm) makes the tags bendable. The presence of the ground plane allows us to isolate the response of the tag from surrounding objects making the proposed configuration suitable for nonplanar lossy objects like filled water bottles or containers. The periodic surface configuration is employed to obtain a sufficiently large RCS to increase the read range of the tags. The proposed tags operate between 26 and 40 GHz, which allows us to achieve the miniaturization necessary for practical scenarios. Toward low cost, thermal printing fabrication is investigated taking lithographic one as a reference. The associated severe loss (introduced by both ultrathin substrate and thermal printing) and the rotation sensitivity of depolarizing label are discussed theoretically and well addressed experimentally. Rotation insensitivity up to 5° and long read range up to 150 cm are experimentally verified. The readability of the proposed ultrathin tags applied to filled bottles is successfully assessed by comparing the performance of tags with and without the ground plane.