Research On RF Energy Harvester For Wireless Sensor Network

In recent years, the deployment of wireless sensor networks become more perfect. However, sensors are typically powered by batteries, and this limits the life of the sensor. This problem can be overcome by using energy harvesting technology to transform the energy from environment to usable electric energy. This technique can be used in various applications, such as remote patient monitoring, implantable sensors, mechanical equipment monitoring. This article describes the RF energy harvesting system, focusing primarily on research rectified RF energy harvesting system architecture, design and select the storage device receiving antenna. In this paper, several rectification architecture, storage devices were compared, and finally completed the design of RF energy harvesting system.Firstly, the article briefly introduces the principle of energy harvesting system, energy harvesting system converts energy from environment to energy that can be used. Then, compare and analyze the piezoelectric, solar, thermal, electrostatic energy, electromagnetic energy, radio frequency energy harvester, comparing the advantages and disadvantages of them, obtaining the result that RF energy harvesting is possibly one way to solve the energy shortage problem now.Secondly, the principles and constitution of RF energy harvesting system was focused, RF energy harvesting system consists of receiving antenna, matching network, rectifier, storage device and load, the most important is the receiving antenna and rectifier circuit. The key issue of RF energy harvesting system is increasing the output voltage and improving power conversion efficiency.Then, the rectifier was compared and analyzed and the same time putting forward some suggestions for improvement. Analyzing the advantages and disadvantages of bridge rectifier and charge pump. Designing a bridge rectifier circuit is so simple, the principle of it is easy, but weak point is the lack of output voltage and power conversion efficiency is not high. However the charge pump has a higher output voltage and power conversion efficiency. In addition, we compared the influence of different stages of the output voltage and power conversion efficiency. Accrording our demanding, we select HSMS-2852 as the charge pump elements.Then, the article focuses on designing of receiving antenna and storage devices. For the receiving antenna, firstly, we designed and simulated single-frequency antenna, finding that single-frequency antenna has a high limitation. Then we designed a multi-frequency antenna to improve the conversion rate of RF energy harvesting system. For storage devices, we exhaustively compared super capacitor and lithium ion batterie, finding that the super capacitor is an ideal energy storage device.Finally, we summarized and discussed the entire radio frequency energy harvesting systems. The design of RF energy harvesting system provides a reference to solve the energy shortage and uninterruptedly supply energy for wireless network. Meanwhile, in future work we hope to find a "super antenna" which can receive energy for each band or different types of energy, to make energy harvesting become a simple and very effective way to use.