Contents I. Introduction
The energy ethernet requires distributed real-time monitoring network to actively sense the states, to define the problems of the system, to discover knowledge, and to solve the problems [1]. This means that more and more sensors need to be integrated into the energy ethernet equipments. Even though the power consumption of both the sensors and the microelectronic chips has decreased in the last decades, life long energy supply is still one of the biggest challenges for the widely distributed and wirelessly enabled sensor systems [2]. A cost-effective and self-sustained monitor system uses energy harvesting to convert unused energy sources into electric power to supply the electronic systems [3]. A variety kinds of energy sources [4], for example vibrations [5], RF energy [6], thermal and solar [7], could be utilized with different techniques, but magnetic energy harvesters based on electromagnetic induction is still the most reliable and cost-effective way to extract energy from the energy ethernet equipment itself [2]. The power line goes through the center of a magnetic core and the 50 or 60 Hz alternating current in the power line will induce voltage on the secondary side, similar manner with a current transformer. What is different with a current transformer is that the output of the secondary winding is feeding a low impedance load to extract energy. Usually a rectifier is followed to converter the AC voltage to DC so that it can power the sensors and microelectronics.
