Pulse Generator Design Of GPR And Research On Phase Based Imaging

In geological research,the applicational value of ground penertrating rader(GPR)is more and more important,for example,in the field of research in geological for researchers.And in the construction field,engineers use the GPR to detect the distribution of underground media.The multiple applications make the requirements for the performance of GPR much more complicated.The GPR transmits high voltage pulse signals and receives the reflected signal from the target,and then analyzes and processes the received signal to form the image of underground environment.The depth of the rader pulse can reach to detect is in relation to the frequency of the pulse.GPRs with Different frequency bands apply to different applictions.However,the traditional GPR only has single frequency band,which can not adapt to more application scenarios.It greatly limits the application value of GPR.As a result,it is a feasible scheme to make the frequency band of GPR adjustable when considering how to improve the adaptability of a single GPR.On the other hand,GPR normally generates the 2D radar image based on the instantaneous amplitude,which is not conducive enough for observation.Considering the electromagetic wave signal will change the phase immediately when through two kind of materials with great difference of electromagnetic characteristics,we propose a new method to image based on instantaneous phase to improve the detecting result.Firstly,this paper intruduces the history and present situation of GPR,the application scene,and the advantges with disadvantages of the traditional GPR equipemnts.Since one single GPR can only provide one frequency band to detect,which greatly limits the applicating of GPR,we propose a new method called Photoconductive Semiconductor Switch based Pulse Synthesis to overcome this disadvantage.In this scheme,we can adjust the frequency of the pulse generated by adding two opposite narrow pulse in timedomain and controling the time delay between them.In this paper,the theoretical derivation and the hardware structure will be intrudued in detail.In this paper,we introduce the traditional imaging method based on instantaneous amplitude,which offen can not provide clear image result.Thus considering the phase mutation when electro-magnetic wave gose through two material with great difference in electromagnetic characteristics,we introduce a new image method based on instantaneous phase.Besides,in order to extract the phase information of signal,we introduce a the empirical mode decomposition(EMD)and Hilbert spectrum.Finally,the simulation experiments are carried out,and the experimental results are analyzed in detail.