Current State of Research at Imperial College London in Rf Harvesting and Inductive Power Transfer

This paper presents simulation and experimental results for ambient RF energy harvesting and Inductive Power Transfer systems. End-to-end and dc-load efficiency measurements and calculations were performed to demonstrate the capabilities of both systems, respectively. An RF spectral survey was conducted across all the 270 underground stations in London. DTV, GSM900, GSM1800 and 3G were selected as the highest contributors and single banded rectennas were fabricated for all frequencies. Ground level measurements demonstrate that more than 50 stations have suitable channel power levels per band to allow ambient RF energy harvesting. Efficiencies of up to 40% were achieved with a single banded rectenna operating at GSM 900, and efficiencies higher than 20% were achieved for TV and 3G. Furthermore a high frequency, semi-resonant Class-E driver was used to transfer 60 W of power across a 30 cm distance with a dc-load efficiency of 66%.