A scalable and multidirectional rectenna system for RF energy harvesting

A rectenna system having multidirectional receiving capability and scalable antenna gain is presented for radio frequency (RF) energy harvesting. The technique of ray tracing was implemented to evaluate RF power collected by antennas with different half-power beam widths. The results indicate that different radiation features are suited to distinct scenarios. This further indicates that a scalable and multidirectional radiation characteristic is highly desired for energy-harvesting antennas because the level of ambient energy varies over time and space. Accordingly, a rectenna system is proposed that can scale in array size, antenna gain, direction of reception, and radiation pattern to enhance conversion efficiency and dc outputs. The proposed device is comprised of five rectenna cells. Each cell consists of a quasi-Yagi antenna with variable numbers of directors and one RF-to-dc energy-harvesting circuit. Thus, the proposed system can achieve either uniform coverage with enhanced antenna gain or highly directional characteristics at one/multiple incidence angle(s). A prototype is designed, fabricated, and tested in terms of each component and the entire system. The experimental results indicate that the proposed system can be useful in various scenarios, and it outputs enhanced power as scaling is performed in the direction of reception and antenna gain.