Design of a 2.45-GHz RF Energy Harvester for SWIPT IoT smart sensors

Simultaneous wireless power and information transfer (SWIPT) is a flexible and cheap way to supply IoT smart sensors avoiding battery replacement. In this paper, we study the design of a 2.45-GHz RF energy harvester (RFEH) system based on a discrete-component matching network, a custom 65nm CMOS cross-coupled rectifier coupled with an off-the shelf storage-charging power management unit (PMU) performing rectifier output voltage regulation with maximum power point tracking (MPPT). For 2.45-GHz operation, we propose a parasitic-aware sizing of p matching network. This introduces a maximum bound on the real impedance at the rectifier input to ensure good impedance matching in practice. MPPT is used to help reaching this target real impedance at given input RF power, as the rectifier input impedance is a function of both its input and output voltages. Measurement results show a sensitivity as low as -17.1 dBm with a peak power harvesting efficiency (PHE) of 48.3% at -3 dBm 2.45-GHz input RF power. Comparison between simulation and measurement results demonstrate that these results are limited by the parasitic capacitance and that PHE around 45% can be obtained down to -10 dBm with PCB/package improvement for lower parasitic capacitance