A quad-band antenna for multi-band radio frequency energy harvesting circuit

In this paper, a compact planar CPW-fed antenna operating over the four frequency bands is proposed for RF energy harvesting applications. The proposed antenna includes five radiating elements and a stepped ground plane, occupies a total area of 48 × 42 mm2. By virtue of stepped ground plane, the antenna exhibits a better impedance match compared to the antenna with the full ground plane. The measured |S11| better than −10 dB is obtained at the frequency bands GSM-900, GSM-1800, Wi-Fi 2.1 GHz and Bluetooth (2.4 GHz), showing its suitability for RF energy harvesting application. For this to be feasible, the developed antenna is matched with the rectifier at four desired frequencies using a compact quad-band matching network. The merit of the proposed rectifier circuit is it can be extended for n number of frequency the band by using only 3n-1 number of lumped elements. To validate the design method experimentally, a prototype of a dual-band rectifier is also fabricated. The measured result demonstrates that the proposed dual-band rectifier circuit achieved the peak efficiency of 42% and 38% for 0.9 and 2.1 GHz, respectively at a load impedance of 4.7 kΩ.