Numerical Simulation Of The Influence Of Signal On The Time-Spatial Focusing Effect Of Time Reversal Electromagnetic Waves

Time Reversal(TR)is an inverse operation of time-domain signals.It can overcome the disadvantage of multipath effect in traditional communication,but make full use of the multipath effect to obtain the effect of spatial multiplexing and adaptive focusing,which is the time-spatial focusing effect.TR technique has wide application prospects in communication,power transmission and high resolution imaging due to its unique time-spatial focusing effect.However,the research of TR technique in the field of electromagnetic wave is still in the initial stage,especially in the research of the influence of signal on the focusing effect of TR electromagnetic wave.In view of the above problems,the main contents of this paper are as follows:(1)The basic theory of TR technique is introduced.Firstly,two important concepts of Time Reversal Mirror(TRM)and multipath effect are presented Then,from the point of view of mathematical theory,the time-spatial focusing effect of TR technique and its corresponding performance characterization are discussed.Finally,the single antenna MIMO effect of TR technique is elaborated in detail.(2)The investigated of signal on the focusing features of TR electromagnetic wave is investigated and the methods to improve the focusing performance are proposed.Firstly,a finite number of TRM array element metal cavity simulation model is established by the use of FDTD electromagnetic simulation tool and MATLAB.Then,simulation experiments on the effects which signal characteristics(waveform,bandwidth and carrier frequency)has on the timespatial focusing effect of TR electromagnetic wave are carried out.Finally,the experimental results show that the signal characteristics have a significant impact on the time-spatial focusing effect of time-reversed electromagnetic waves.Choosing the appropriate signal type or improving the signal bandwidth can enhance the time-spatial focusing performance of TR electromagnetic waves.(3)The effect of signal on the number of effective multipaths in TR single antenna MIMO effect is investigated and a method to increase the number of effective multipaths is proposed.Firstly,the spatial channel impulse response is obtained by simulation and experiment.Finally,the influence of the number of effective multipaths on the channel is analyzed.The experimental results show that increasing the signal bandwidth can effectively increase the number of effective multipath channels and achieve better performance of TR single antenna MIMO.