Research On Multi-frequency Multi-focus Wireless Power Transfer Based On Time Reversal

With the rise of the Internet of Things,lots of smart sensor devices have emerged in indoor environments such as smart factories,smart homes,and unmanned workshops.However,how to ensure the long-term and stable energy supply of a large number of electronic devices in the room is the key to achieving the Internet of Everything.The traditional cable method not only greatly limits the flexibility and convenience of energy supply,but also has potential safety hazards in the intricate wiring.To this end,with the unique space-time focusing characteristics of Time Reversal(TR)technology,a new point-focused Time Reversal Wireless Power Transfer(TR-WPT)method was developed,which is expected to a large number of sensors and other user devices energy supplying problems.However,when selective energy transmission is performed for multi-users,the existing TR-WPT energy transmission method cannot achieve continuous energy transmission with high energy efficiency and low side lobe.In addition,the side lobe crosstalk caused by the coupling effect of adjacent users limits the distance between the users that can be received,so that the capacity of the users in the energy transmission space cannot be further increased.Therefore,for the above two unsolved problems,this thesis proposes two different solutions,which lay a solid foundation for promoting the wireless energy transmission of a large number of user devices in the indoor environment.First,based on the working principle of WPT,a multi-frequency single-link energy transmission mathematical model is constructed,the relationship between efficiency and frequency under complex multi-path frequency-selective channels is studied,and the internal mechanism of TR signal return focusing is theoretically analyzed.Secondly,a multi-frequency multi-focus WPT method based on TR is proposed.Based on the constructed TR multi-frequency multi-focus WPT mathematical analysis model,the multi-frequency selective method is theoretically studied.At the same time,the TRM excitation signal optimization method considering side lobe,efficiency and power distribution is studied,and the specific TR multi-frequency multi-focus WPT implementation scheme is given.Next,the indoor transmission space was simulated with a rich multi-path cavity model.Using electromagnetic simulation and numerical analysis,the effect of the TR multi-frequency multi-focus WPT method on energy transmission performance was studied.Compared with single-frequency TR-WPT,the advantages of TR multi-frequency multi-focus WPT in solving the high energy efficiency and low side lobe selective energy transmission of multi-users are confirmed.Finally,to solve the problem of the limited number of multi-users caused by the coupling of adjacent users,a TR-based WPT method of frequency division multi-focus is proposed.From the theoretical analysis and simulation calculations,it is proved to be feasible in solving the capacity of the multi-users.