Design Considerations of Antennas and Adaptive Impedance Matching Networks for RF Energy Harvesting

This paper reviews recent developments in design of antennas and impedance matching networks for RF Energy Harvesting (RF-EH) at UHF. The antenna design is considered in conjunction with the requirements that it places on the impedance matching network (IMN), in order to match the load which is an RF to DC converter. It is shown that there may be advantages in using an interface impedance between the antenna and the IMN that differs from the conventional 50 Ω impedance. Various options are considered for the design of an IMN driving a rectifier load. A novel adaptive IMN architecture is proposed that can match two different load impedances, depending on the received power level. This can optimize Power Conversion Efficiency (PCE) over a range of different input powers that may be encountered in RF EH.