Method And Technology Of Wirelessly Driven LED Screen Based On Focusing Mechanism Of Time Reversal

Wireless power transfer(WPT)is a research hotspot in recent years,which can transfer energy from the source to the load wirelessly or without cables.WPT can significantly improve the convenience and safety of transmission,and can be applied to the special occasions where power lines are difficult to set up,like implantable medical device charging,continuation of near-earth drones and emergency rescue in disaster areas.However,in practical applications,due to the influence factors such as the distance of transmission,the efficiency of powering,the environment of energy transmission,the safety of electromagnetic radiation,etc.,wireless powering cannot be widely promoted.In addition,it is still a challenge to selectively transmit wireless energy to single or multiple targets.In view of above problems,this article put forward a spot-focused WPT method based on time reversal(TR)electromagnetic focusing field for high-efficiency,selective and multi-target charging,and then conducted in-depth research on its key technology and characteristics.First,a focused WPT technology based on single-frequency time reversal is proposed,which overcomes the disadvantages of pulse wave TR technology in energy transmission instability and physical implementation difficulties.Currently reported TR technology and its applications use short-time pulses as the excitation source basically,and the concentration of space energy only occurs at a specific moment.For power transmission applications,continuous and stable energy transmission is required,conventional TR techniques cannot be applied directly.In this paper,a sine wave is used as a TR transmission signal,and the energy reception waveform is a sine wave with uniform amplitude too.On this occasion,time reversal can be equivalent to phase conjugate,which can significantly reduce the physical difficulty and cost of TR operation in the RF and microwave frequency bands.Secondly,this paper established a theoretical analysis model of single-point focused WPT.And the space energy efficiency of TR-WPT was researched.Results show that the TR scheme is the best option which can get highest spatial energy efficiency.Then,a TR multi-point focusing field based on the TR technique and the principle of linear superposition is optimized.This focusing field only delivers equivalent energy to selected targets and can prevent wireless energy being stolen by other targets.It means that the key technical problem of multi-target and selective WPT is solved.Finally,a WPT system based on the TR focusing mechanism was successfully constructed,and the system can drive one or more LEDs wirelessly to form the desired dot matrix display pattern.Experiment shows that the space energy efficiency between receive and send antennas can be up to 70% or more,which verifies the feasibility and superiority of the spot-focused WPT method proposed in this paper.