Wireless Power Transfer of Passive UHF RFID Uplink in the Case of Tags Network

The RFID (Radio Frequency Identification) technology is evolving strongly with the emergence of cognitive sensor networks and notably the Internet of Things. A significant indicator of this evolution is that the tags are equipped with new capabilities and functions such as more powerful sensors, actuators, etc. This evolution of the RFID requires more energy consumption, and the continued passive nature of tags could be threated. Indeed, the tag needs more and more energy, and the energy received from the only reader can be insufficient. To address this issue, the proposed concept is to exploit the reflected energy by the tags near to the “target” tag. In this paper, we develop the associated theory for far-field conditions. The theoretical development is illustrated and the impact of the relative position between the tags on the total energy captured by the “target” tag is emphasized.