Rectenna Designs for RF Energy Harvesting System: a Review

In this paper, a review of different types of rectifying antennas (rectennas), used for harvesting RF ambient signals, is presented. This work focuses on rectenna design as one important technique of wireless energy transfer. The most important parameters in rectenna design such as conversion efficiency, rectenna size, antenna gain and polarization, rectifier element, and overall performance of the rectenna are studied and compared. It is noted from studies that rectenna design suffers from low conversion efficiency and large size which limit their use in wireless applications. Therefore, to overcome the above mentioned limitations, some techniques such as microstrip antenna with, a metamaterial structure, harmonic suppression and circular polarization properties can be suggested. A voltage doubler rectifier can be used with the metamaterial microstrip antenna to improve the conversion efficiency of the rectenna. Hence, High efficiency and small size of the rectenna will enable the rectenna to produce sufficient DC voltage and current to charge batteries used in medical applications and wireless sensors applications as well.