Planar U-Shaped Slot Multiresonator-based Chipless RFID Tags

The paper introduces the design for chipless Radio Frequency Identification (RFID) tags aimed at facilitating broad-band detection, tracking and identification tasks. The tags are realized on RT 5880 substrate having a relative permittivity of 2.2, a loss tangent of 0.0009 and a thickness of 1.575 mm. Constructed with 6 U-shaped slots arranged on the substrate, each slot functions as a resonator contributing to the tag’s overall response to incident electromagnetic waves. To evaluate tag performance, the Radar Cross-Section (RCS) responses are analyzed, giving 6 distinct resonances with adequate resolution. This suggests the tag’s capacity to differentiate between frequencies or states corresponding to the encoded bits. The design process leverages CST Microwave Studio to optimize parameter’s and achieve desired performance characteristics. With concise dimensions of $20 \mathrm{~mm} \times 20 \mathrm{~mm}$, the tags are conducive to integration into diverse objects or systems. The tag functions in the frequency range 4.25-8.94 GHz covering a bandwidth of 4.7 GHz. The paper also discusses the coding technique used to encode the stored data in the tag, namely ’absence or presence’ coding and the effect of propagation vectors kept in different orientations of the exciting signal on the tag.