Design Of Multiband Energy Harvesting System For Mobile Communication Base Stations

With the rapid development of RF and wireless sensor network technique,the wireless sensor network has gotten very good application in many fields.But the battery is still its main node power supply and waste batteries can cause environmental pollution,maintenance and replacement of batteries become bottlenecks.RF energy harvesting technique can harvest ambient RF energy to convert DC output.It can assist even replace batteries for low-power devices,which is a very good option to realize the passive sensor node.With the growing band of mobile communications,RF energy harvesting multiband problems should be considered.And,honeycomb is more and more small and mobile communication base station is more and more intensive,which forms multiple wave directions.For harvesting energy as much as possible from the mobile communication system,how to look for the biggest wave direction and how to harvest RF energy efficiently from multiple base stations at the same time,which are the keys of this paper studied.According to the distribution characteristics of mobile communication base station,this paper proposes an RF energy harvesting system with multiband for base stations.It includes dual-band energy harvesting antenna and conversion circuit,a coming wave direction system,and a device of energy harvesting for multiple base station.Dual-band energy harvesting antenna and conversion circuit are designed.A coming wave direction system based on zero point alignment is designed for wave detection.And,a device adjusted easily is designed to harvesting RF energy from multiple stations.The main contents of this paper are as follows:Firstly,the background and significance of RF energy harvesting technique is introduced,and the research status is analyzed.The block diagram of RF energy harvesting system for mobile communication band is presented.Secondly,dual-band harvesting antenna is designed for mobile communication bands by analyzing the similarities and differences between RF energy harvesting antenna and ordinary antenna.The three-dimensional and crossed array way is presented to improve efficiency,and easy array dipole like flower is designed to verify its possibility.Thirdly,diode selection,matching circuit design and circuit form of conversion circuit are analyzed.Frequency division conversion circuit and resonant conversion circuit are studied.And the advantages and disadvantages of these two dual-band conversion circuits are summarized.Fourthly,a coming wave direction system is developed for characteristics of mobile communication base station.Zero positioning antenna is based on zero point alignment technique,two step motors form the antenna rotating platform,and the software of Msp430 and PC interface based on C# are developed.The system test shows that the direction of coming wave can be found by using the system to ensure the accuracy of energy harvesting direction.Finally,the effectiveness evaluation of RF energy harvesting system is given to test harvest efficiency,circuit efficiency and rectify efficiency.And,a device is designed for multiple stations to harvest mobile communication bands with three RF energy harvesting and battery management circuit.Steady voltage output is obtained in field measurement.In conclusion,this paper realizes multiband energy harvesting for base stations,based on a coming wave direction system to analyze characteristics of mobile communication base stations.The results show that the system is feasible,and it provides a new way for passive power supply of wireless sensor nodes.