Wireless power harvesting with planar rectennas for 2.45 GHz RFIDs

This paper presents a rectenna (rectifier + antenna) design to harvest electrical energy for powering RFIDs from ambient electromagnetic radiation at the 2.45 GHz ISM band (WiFi, Bluetooth, RFID, etc.). The rectenna structure is formed by a miniaturize 2
^nd
iteration Koch fractal patch antenna and two stage Dickson charge pump voltage-doubler rectifier circuit. The proposed rectenna achieves a small size with relatively high realized gain (4 dBi) and good RF to DC conversion efficiency (up to 70%). As a result, the proposed rectenna harvests enough energy from a commercial RFID interrogator 3.1 meters away (4W EIRP at 2.45 GHz ISM band) to power up a 1.6 V LED, enough voltage to enable some RFID chips.