Research On Uniform Wireless Power Transfer Of Multi-targets Based On Time Reversal

Under the background of the comprehensive commercial use of 5G technique and the rapid development of 6G technique,the vigorous development of internet of things(Io T)technology has promoted the progress of smart homes,smart factories and smart railways.However,the charging problem of various smart sensors in Io T devices still needs an efficient and stable solution.Therefore,exploring the wireless power transfer(WPT)technique used in different scenes to achieve efficient,robust and uniform WPT of massive sensors is a development need for future Io T applications.Time reversal wireless power transfer(TR-WPT)technique has the advantages of highpower transfer efficiency,wide power transfer range and good safety,and also has the potential to solve the charging problem of large-scale intelligent sensors.However,when using TRWPT technique for multi-target power transfer,there will be the problem of the "near-far effect",high side lobe levels and power focusing accuracy decreasing.Aiming at the above problems,this thesis proposes solutions from two aspects: time reversal(TR)signal processing and time reversal mirror(TRM)distribution.In terms of TR signal processing,an automatic zone selection channel matching method based on the channel compensation are proposed to achieve high-precision,long-time,uniform and constant WPT of multi-target.In terms of onedimensional TRM distribution,the performance of the coprime array as a power-transfer array is studied,and it is proven that the coprime array has better power transfer efficiency.At the same time,the selection method of the optimal expectation power transfer array with large aperture is proposed.In terms of two-dimensional TRM distribution,the concept of equalspace angle large aperture is proposed,and it can solve the problems of high side lobe level,low power transfer accuracy and low focusing resolution of traditional power-transfer array in WPT application.This thesis’ specific research contents are as follows:First,the basic principle of TR technique is introduced,the reciprocity of Green’s function and the time symmetry of the wave equation are proved,and the physical mechanism of TR technique’s spatiotemporal synchronous focusing is explained.At the same time,the multitarget power transfer result of TR-WPT technique is deduced,and the causes of power nonuniformity at different target positions are analyzed.Second,the automatic zone selection channel matching method based on the channel compensation is proposed.In the background environment of free space,the numerical experimental results of TR technique,channel compensation method and automatic zone selection channel matching method are analyzed and compared.It is proven that the proposed method can achieve high-precision,long-time,uniform and constant multi-target power transfer.Then,using the metal resonant cavity as the background to simulate the complex multipath electromagnetic environment.In this environment,comparing the power transfer performance of coprime array and uniform linear array,highlighting the advantages of the coprime array and a selection method of the optimal expected power transfer array with large aperture is proposed.Finally,the concept of equal-space angle with large-aperture is proposed.In the background environment of free space,the WPT performance of the equal-space-angle largeaperture array as a power-transfer array is studied.Compared with the traditional twodimensional uniform array,it is verified that the equal-space angle large-aperture array can effectively improve the traditional power-transfer array’s the side lobe level,power transfer accuracy and focusing resolution in WPT application.