The Study Of Microwave Energy Transfer's Precoding Technology And Electromagnetic Radiation Safety

With the wide application and distribution of various electronic devices,there is also an increasing demand for contactless charging and energy delivery.In order to solve the problem that cables are difficult to deploy and the energy transmission sustainability is poor in a specific application scenario,wireless energy transmission technology is gradually developed.The microwave energy transfer technology is a wireless energy transfer technology that converts electrical energy into microwaves.The microwaves pass through the free space to the energy receiving end,and then rectify and convert into electrical energy.The microwave energy transmission system has a long transmission distance,and the energy of propagation is high and the frequency is high.In the transmission process,it is easy to cause interference to the communication equipment in the surrounding environment,and the electromagnetic wave with high energy density is bound to have an impact on personal safety.Therefore,the electromagnetic compatibility and electromagnetic radiation safety of the microwave energytransmission system cannot be ignored.Simultaneous Wireless Information and Power Transfer System(SWIPT)is a cooperative information and energy transmission system based on microwave energy transmission technology.The system relies on different working modes of the receiver and can be divided into two modes of information transmission and energy collection.The system performance indicators of the two modes are different.The performance optimization under the two modes is the focus of the research on the simultaneous signaling system.The specific contents include:(1)Firstly,this paper analyses the SWIPT system model based on multi-user MIMO.Receivers receive information and collects energy in different time slots.In the information transmission mode,the system aims at maximizing the information transmission rate.In the energy collection mode,the system aims at maximizing the energy collection.In order to optimize the performance of SWIPT system,the transmission strategy of maximizing channel capacity and energy collection strategy are analyzed according to two working modes.The effects of different precoding algorithms on the performance of SWIPT system are analyzed thr-ough simulation,and the optimal precoding mode is selected for different working modes of SWIPT system.In order to improve the system performance of user QoS,a QoS evaluation model of multi-user SWIPT system service is established,and a service selection strategy of multi-user SWIPT system based on QoS is proposed,which can meet the user's QoS and realize the rational utilization of system resources.It has reference significance for improving the resource utilization efficiency of SWIPT system.(2)For the electromagnetic compatibility of the microwave energy transmission system,the microwave transmitting antenna model was first selected,and the electromagnetic radiation value of the microwave energy transmitting antenna was evaluated according to international standards.Since the electromagnetic wave emitted by the microwave energy transmission system has a high frequency and the electromagnetic wave carries a large amount of energy,it is easy to cause blocking interference to the communication system in the electromagnetic environment.Based on the electromagnetic compatibility prediction principle and analysis model between systems,the electromagnetic compatibility between the microwave transmitting system and the Wi-Fi communication system in the adjacent frequency band is studied.This paper innovatively uses ANSYS EMIT software to perform system-level electromagnetic compatibility simulation of microwave energy transmission system and Wi-Fi communication system,analyzes the generated blocking interference,and proposes electromagnetic compatibility protection measurements.It has reference significance for the electromagnetic compatibility design when the microwave energy transmission base station is deployed.(3)In view of the safety of electromagnetic radiation in microwave energy transmission systems,this paper first analyzes the adverse effects of electromagnetic radiation on the human body.Based on the selected microwave energy transmitting antenna,the CST simulation platform is used to simulate and predict the SAR value(specific absorption rate)of the human head in the environment around the microwave energy transmitting base station.In addition,according to the international safety regulations for human body radio frequency exposure,the safe area of human electromagnetic exposure in the microwave energy transfer environment is delineated.An automatic prediction software for safe distance of electromagnetic radiation is designed.The electromagnetic protection safety distance of the base station can be calculated and obtained according to the input antenna parameters of the base station,which is of reference significance for the deployment and design of the base station for microwave energy transmission.