volume | PIER Journals

Abstract

This paper presents a proximity-activated UHF RFID tag based on a discrete-component architecture aimed at enhancing user privacy at the physical layer. The RFID chip is physically separated from the main meandered dipole antenna and mounted on a detachable coupling loop. Tag activation occurs only when the loop is positioned at approximately 1 mm from the antenna, enabling near-field inductive coupling and conjugate impedance matching. In the default configuration, the chip remains effectively unreadable, while selective activation is achieved by applying the external coupling loop when tag interrogation is required. Two coupling-loop geometries are investigated: a simple rectangular loop and a multi-turn spiral loop, both integrated with capacitively loaded dipole antennas optimized for the European UHF RFID band at 866 MHz. Full-wave simulations confirm the intended on/off behavior, with minimum reflection coefficients of -34.8 dB at 866.7 MHz and -31.1 dB at 867 MHz, respectively. When the loop is removed, both designs exhibit severe impedance mismatch across the operating band. Experimental results validate the proposed concept. The rectangular loop achieves a peak read range of 6.0 m, while the spiral loop reaches 0.7 m. Misalignment tests indicate that both configurations maintain functionality under practical lateral and vertical offsets. Overall, the rectangular loop provides a wider and more robust activation region, making it suitable for applications requiring controlled, on-demand RFID readability for product authentication and quality verification without continuous exposure to RFID tracking.

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Dr. Hamza Othmani

Dr. Mohamed Karim Azizi

Dr. Luca Catarinucci