Design and realization of a wearable multi-frequency RF energy harvesting system

In this paper a novel wearable, triple-band ring-antenna, designed to harvest RF energy from GSM 900, GSM 1800 and WiFi sources available in the ambient, is introduced. It consists of a single annular ring suitable modified with appropriate slots to be operated as a resonant radiator at all the bands of interest. This choice allows us to achieve high radiation efficiency and circular polarization in compact dimensions, compatible with technology garments. A rectenna is then designed by the concurrent use of harmonic-balance technique and electromagnetic simulation to predict the real rectified power in general operating conditions. A multilayer configuration is exploited making use of textiles and flexible substrates whose integration issues are also discussed.