Development of a Wireless Power Transmission System for Embedded Passive Sensors Using LF RFID Technology

Wireless power transmission (WPT) can be used to enable full embedding of sensor systems and thus remove the need for wired connections and batteries. In this paper a WPT system based on inductive coupling at 125 kHz is presented. The main design considerations that must be taken into account when designing such a system will be presented. This includes the design of the power transmitter and the power receiver as well as the fabrication of proper antennas. The proposed system architecture has been completely implemented and measurements have been carried out for validation. It is demonstrated that the fabricated system achieves a wireless transmission of 10.4 W at a 5 cm distance with 69 percent efficiency and 7.9 W at 10 cm distance with 30 percent efficiency. In order to facilitate the integration of the wireless system, a new version of the antennas and the PCB have been fabricated. Two different prototypes are built with two different antenna coil thickness's. The obtained results corroborate the importance of the selected wire resistivity, since 5.9 W and 9.5 W are obtained for 0.5 mm and 1 mm thickness respectively at a 5 cm distance. A first prototype has also been fabricated to prove that the WPT electronics can be successfully embedded into the composite.