Research On Key Technologies Of Movable-Focus Wireless Power Transmission Based On Time Reversal

The application of a large number of sensors is the key to the development of smart home,intelligent manufacturing and other industries.The power supply problems of these sensors gradually expose the disadvantages of the traditional wired energy transmission mode,such as complex wiring,cable damage,poor flexibility and so on.Especially when the number of equipment is large,the power supply cables are easily intertwined with each other,and the aging of cables will also bring great security risks.In some scenarios where the equipment needs to be moved,wired power supply will bring great inconvenience.Time reversal wireless power transmission(TR-WPT)has the advantages of long energy transmission distance,high efficiency,good security,good flexibility and so on.It is expected to truly solve the problem of large-scale sensor power supply.However,the current TR-WPT technology uses a fixed TRM.On the one hand,when the position of the receiving target changes,the efficiency of WPT and the receiving power of the receiving antenna will also change,resulting in the instability of WPT;on the other hand,when the distance between the transmitter and receiver is relatively close,too many transmitting units will lead to the low efficiency between the transmitter and receiver.In view of the above problems of TR-WPT technology,this paper proposes a movable-focus wireless power transmission technology based on TR-WPT.When the position of the receiver changes,adjusting the number of TRM units can not only make the efficiency between the transmitter and receiver always in a high state,but also stabilize the power of the receiver.This technology can provide a basis for power stability and efficiency improvement under dynamic transmission.The specific research contents are as follows:Firstly,the theory of discrete time reversal is introduced,and the focusing mechanism of discrete time reversal is deduced.The time reversal theory of TRM array is deduced when TRM array is planar array.Finally,the relationship and difference between time reversal(TR)and phase conjugation and the realization of TR of single frequency signal are introduced.Secondly,according to the radiation equation of point source in free space and the electromagnetic focusing principle of TR,the theoretical model of TR-WPT based on planar time reversal mirror is established.According to this model,the efficiency calculation formula of TR-WPT in free space is derived,and the efficiency calculated by this formula is compared with Friis transmission formula and full wave simulation results,The advanced and accuracy of the formula is verified.Then,by using the formula of TR-WPT efficiency derived above,the influence of TRM array aperture,energy transmission distance,receiving aperture and other factors on TR-WPT transmission efficiency in the case of single target is studied,which provides a theoretical basis for the realization of movable-focus power transmission.Finally,the accuracy of the movable-focus algorithm proposed in this paper is verified by comparing the actual energy transmission unit selected by the efficiency formula and the active transmission unit selected by the algorithm proposed in this paper.The effect of movable-focus power transmission on the stability of transmission power is studied.