Measurement Platform for Electromagnetic Characterization and Performance Evaluation of UHF RFID Tags

Abstract

The huge improvement in UHF radio-frequency identification (RFID) technology, also driven by the vision of the Internet of Things, is leading to a widespread diffusion of several kinds of passive RFID tags. In fact, depending on the specific application, tags must satisfy key requirements in terms of size, thickness, shape, robustness, cost, working range, bandwidth, antenna directivity, platform tolerance, polarization, and so on. In such a scenario, the design of a specific application-oriented tag by an RF designer as well as the careful selection among commercially available solutions by system integrators rather than final users needs a dedicated measurement system enabling a rapid and cost-effective procedure for the on-air performance evaluation of RFID tags. Nevertheless, the design of such a system is not trivial, as tag performance depends on multiple major factors, such as chip sensitivity, quality of the chip-antenna conjugate matching, and antenna radiation properties. In this paper, after a theoretical formulation, an accurate, flexible, robust, and cost-effective RFID tag characterization and performance evaluation platform is presented and validated. It allows the calculation of the main metrics characterizing an RFID tag as a function of the tag activation power threshold when varying both interrogation frequency and tag orientation. The system is validated on both specifically designed and commercial RFID tags in terms of sensitivity, working range, and tag antenna radiation pattern: measurements show strong agreement with the theoretical and simulation results.