Far-field RF energy transfer and harvesting

This chapter deals with radio frequency (RF) energy transfer over a distance. After explaining the differences between nonradiative and radiative RF energy transfer, the chapter gives definitions for transfer and harvesting. Nonradiative RF energy transfer is mostly employed in inductive systems, obeying the Qi standard. The chapter also identifies the subcomponents of an RF energy transfer system, and discusses the receiving rectifying antenna, commonly known as rectenna. Before discussing the rectenna results, the chapter discusses the complex conjugately matched antenna. After that, the transmission and propagation of RF signals is treated, followed by demonstration of some examples of far-field wireless RF energy transfer. It concludes that far-field RF energy transfer is feasible, but requires a careful co-design of the several subsystems that make up the whole far-field RF energy transfer system.