Novel Fabrication-Tolerant Resonator Design for mm-Wave Chipless RFID and Its Analytical Model

This paper presents a class of novel fabrication-tolerant resonator design for high-capacity chipless RFID tags. The proposed resonator is based on a high-quality-factor grounded dipole with a single etched slot of variable length. By controlling the slot length, the resonant frequency can be adjusted while exhibiting much lower sensitivity to design variables compared to conventional dipole resonators. This makes the design resilient to fabrication tolerances, a critical requirement for mm-wave frequency bands. This feature enables a two-step fabrication process: first, producing high-precision master tags (e.g., via roll-to-roll fabrication), and second, customizing them by etching slots using a flexible method like laser etching. The presence of a ground plane provides isolation from the tagged object, enabling application to diverse materials and geometries. An analytical model is derived to establish the relationship between slot length changes and resonant frequency shifts, enabling efficient design optimization. Sensitivity analysis shows the proposed resonator has a single parameter sensitivity of 0.008 (feasibility), and overall sensitivity of 0.04 (stability) under $\pm 50\;\mu\text{m}$ fabrication tolerance, over two orders of magnitude and half lower than the sensitivity of 1 for conventional dipoles. The resonator design is validated through simulations and experiments, demonstrating its potential for high-capacity, fabrication-tolerant chipless RFID tags.