3-D Maximum Power Point Searching and Tracking for Ultra Low Power RF Energy Harvesters

Radio-frequency (RF) energy harvesting must cope with the limited availability and high variability of the energy source. In this paper, the modeling of an RF harvester for ultra low power environments is presented. Simulation results and theoretical analysis demonstrate that the maximum transferred power point is located in a three-dimensional space defined by the input capacitance, the output voltage, and the load resistance of the rectifier circuit. The paper proposes also the implementation in ST 65 nm CMOS technology of a mixed signal system for the 3- D MPPT, to be embedded in an RF harvester. The circuit exhibits a simulated power consumption lower than 100 nW, making this solution suitable for ultra low power harvesting.