This paper presents the design and measurement of an RF energy harvesting and power management unit that operates across a wide range of available input power, from-24 to +15dBm. The system comprises an adaptive impedance matching network, a single-stage cross-coupled differential-drive rectifier, a start-up charge pump, an adaptive buck-boost converter, a maximum power point tracking (MPPT) circuit and a control loop to regulate the load voltage. The MPPT circuit controls the switching frequency of the buck-boost converter and configures the impedance matching network, optimizing the interfaces between the rectifier and antenna and between the rectifier and the storage capacitor, guaranteeing that the power is being harvested at maximum efficiency. To boost the rectifier output, to accumulate energy in the storage capacitor and to provide energy to the load, a single-inductor buck-boost converter that has two inputs and three outputs is used. Circuit techniques that reduce the power consumption of the control circuits and that allow for adapting the interfaces between the antenna, the rectifier and the load are presented. The peak harvesting efficiency of the system is 40.2%, when presented with an RF source of-9.1dBm available power and 403.5MHz frequency.

In this paper we present the design and simulation results of an RF energy harvesting circuit that operates across a wide range of available input power, from -27 dBm to 6 dBm. The system comprises an adaptive impedance matching network, a single-stage cross-connected differential rectifier, a start-up charge pump, an adaptive buck-boost converter and a Maximum Power Point Tracking (MPPT) circuit. The MPPT circuit controls the switching frequency of the buck-boost converter and configures the impedance matching network, optimizing the interfaces between the rectifier and antenna and between the rectifier and the storage capacitor, thereby guaranteeing that maximum power is being harvested. The system is designed in a standard 0.18 pm CMOS technology. The peak efficiency is 49.1% at an available input power of -18 dBm and signal frequency of 403.5 MHz.