Distance-sensitive High Frequency RFID Systems

Location information about a high frequency RFID tag is currently limited to the location information associated with the position of the RFID reader. The distance of a tag from the reader remains unknown. However, more precise location information of objects provided at low cost is critical to create smart spaces. In this paper, we present a distance-sensitive RFID system that accurately resolves a tag's distance from the reader. In contrast to other distance sensing systems that operate on the emission of electromagnetic waves, high frequency RFID systems make use of magnetic coupling for data transmission. The paper details the system design and implementation with discrete components, presents the distance measurement procedure, and evaluates the accuracy of the measurements.