A corner-slit ring resonator chipless RFID tag with validated performance on curved metallic surfaces for product identification and tracking

Existing chipless RFID tags are constrained by limited encoding capacity and read range, motivating compact, cost-effective, high-density designs for scalable product tracking. This work presents a 1–6 GHz chipless RFID tag comprising 18 concentric square ring resonators with corner slits, fabricated on a low-cost FR-4 substrate (70×70 mm, εr=4.4, tanδ=0.02). A geometric corner-slit-loading strategy yields 13 distinct resonant dips in the simulated monostatic RCS spectrum on a flat substrate. When conformally mounted on a cylindrical metallic surface, measurement of the forward transmission coefficient S21 reveals 14 spectral dips; rigorous harmonic and artifact analysis confirms 13 as valid data states. Mutual coupling and spectral overlap are mitigated through full-wave iterative electromagnetic optimization in CST Microwave Studio. The simulated spectral and area efficiencies are 2.6 bits/GHz and 0.265 bits/cm 2, respectively. In the conformal metallic environment, measured efficiencies are consistent at 2.6 bits/GHz and 0.265 bits/cm 2, with minor Q-factor degradation attributable to the metallic ground plane. Benchmarking confirms this design outperforms existing conformal chipless RFID tags in bit capacity at an 83 cm far-field read distance, demonstrating suitability for real-world, scalable product tracking on metallic surfaces.