Internet of Things (IoT) is an emerging platform in which every day physical objects provided with unique identifiers are connected to the Internet without requiring human interaction. The possibilities of such a connected world enables new forms of automation to make our lives easier and safer. Evidently, in order to keep billions of these communicating devices powered long-term, a self-sustainable operation is a key point for realization of such a complex network. In this sense, energy-harvesting technologies combined with low power consumption ICs eliminate the need for batteries, removing an obstacle to the success of the IoT. In this work, a Radio Frequency (RF) energy harvester tuned at AM broadcast has been developed for low consumption power devices. The AM signals from ambient are detected via a high-performance antenna-free LC circuit with an efficiency of 3.2%. To maximize energy scavenging, the RF-DC conversion stage is based on a full-wave Cockcroft–Walton voltage multiplier (CWVM) with efficiency up to 90%. System performance is evaluated by rating the maximum power delivered into the load via its output impedance, which is around 62 μW, although power level seems to be low, it is able to power up low consumption devices such as Leds, portable calculators and weather monitoring stations.

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2015) RF energy scavenging system for DC power from FM broadcasting based on an optimized Cockcroft-Walton voltage multiplier,The potential utilization of RF signals from a commercial FM band (88-108 MHz) is explored for DC power. In this paper, an RF energy scavenger has been developed which is able to power up low power consumption devices. The RF-DC conversion stage is based on a six-stage Cockcroft-Walton voltage multiplier (CWVM), and its performance is analyzed by rating the maximum power delivered in the load via its output impedance. Several models have been previously proposed in order to predict the output impedance of CWVMs in lieu of optimizing the maximum power delivered to the load; nevertheless all of them were inaccurate. Here, a new approach based on the CWVM transmission line model, which accurately predicts output impedance, is proposed. Under this framework, the output impedance of the CWVM depends only on junction capacitance and resistance of the diodes rather than stage capacitors, as considered formerly.

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