An Impedance Matching Strategy for Micro-Scale RF Energy Harvesting Systems

Radio frequency (RF) energy harvesting is widely adopted as an alternative source of energy to power a wireless sensor node or an Internet of Things (IoT) node. In order to extract maximum power from an RF energy source, variations in an RF to DC converter (RDC) input impedance with input power should be taken into account. This brief demonstrates that a tunable impedance matching strategy is essential to track the changes in input impedance to ensure maximum power transfer across the desired input power levels. A two-state tunable matching network is proposed to track variations in input impedance with the input power of an RDC with a load of 10 k Omega, and at an operating frequency of 953 MHz. The proposed impedance matching network and the RDC are designed using 0.18-mu m CMOS technology node. Circuit simulations demonstrate that the proposed matching strategy extends the input power range over which maximum power transfer occurs by 5 dBm and 13 dBm in comparison to a fixed matching network designed at -24 and -18 dBm, respectively.