Design and reliability evaluation of passive HF RFID systems in metal environments

In spite of the popularity of passive Radio Frequency Identification (RFID) systems, reliability is an important topic to achieve the adoption of this technology in certain areas of applications. Maintaining this reliability is especially challenging in applications where metals are ubiquitous. This article describes how a passive HF RFID system is optimized for implementation within a closed metal case. The ideal orientation of a transponder within a metal environment is determined. Various simulations were executed in order to predict the areas where the magnetic field exceeded the activation field of the tags. The findings, resulting from these simulations, are verified by hardware measurements which show high prediction accuracy for the practical test setup. In this paper we optimized the reliability of RFID systems by adjusting the radius of a circular loop antenna to the metal construction. In future work, the simulation and measurement tools presented here will be used to evaluate and, eventually automatically generate, optimal antennas with other (non-circular) shapes for different environments.