A Wideband Fractal Antenna and Comparison of RF Rectifiers for Electromagnetic Energy Harvesting

Abstract

This paper presents a wideband fractal antenna and compares two efficient rectifier topologies suitable for 2.45 GHz band. The combined fractal antenna and the rectifiers may be used for ambient RF energy harvesting from wireless LAN/Wi-Fi. The proposed fractal antenna covers the most frequently encountered frequency bands which are located around 1800 MHz, 2.1 GHz, 2.4 GHz and 2.45 GHz corresponding to standards like GSM/DCS, UMTS, ISM and WLAN respectively. The return loss of the proposed antenna is below −10 dB and its gain is 4 dBi between 2.40–2.47 GHz. Two different Greinacher voltage tripler rectifier circuits were designed to compare the RF to DC conversion efficiency and power handling capability of the rectifying circuit structures. Up to 60% power efficiency was achieved with the proposed rectifiers at 2.45 GHz.