Multiport RF energy harvesters -

Abstract

RF energy harvesting allows the transformation of wireless RF energy into collectable dc power and constitutes the basis of green wireless charging and energy transfer technology. Various components, such as deployed sensors and small portable devices benefit from this technology to power their continuous operation. Harvesting low powered RF signals and rectifying them into a notable dc output is a challenging task. Such task requires understanding of the rectifying component’s limits to maximize the desired outcome. The aim of the work presented in this thesis is to design an efficient RF energy harvesting system for low input power levels operating over the Wi-Fi 802.11 b-g band. We propose a novel design of RF harvesters and rectifiers solely based on using zerobias Schottky diodes. Our design objective is to identify the most suitable technique that results in an increased output dc power while maintaining the same transmitted power from the RF source. A tradeoff analysis is executed between various matching networks for better rectification efficiency and dc output. Our designed rectifiers prove the ability to harvest and rectify the RF signals with a very good efficiency across a multitude of frequencies. We have then integrated these circuits into a multiport RF energy harvesting system that relies on two combining architectures: RF combining and dc combining. The multi-port rectifier system demonstrates excellent harvesting capabilities with an increased output dc voltage in both combining scenarios. We also discuss the harvesting of very small RF energy from ambient Wi-Fi signals that are collected from commercial Wi-Fi routers. The rectifier is tested in ambient conditions and efficiency results display a comparable performance to harvesting from dedicated RF signals. In this thesis, Support Vector Machines (SVM) is also employed to yield a system that can predict with a good accuracy the location and level of maximum power available at a certain day and time. In summary, the limits of Schottky d