Research On Imaging Technology Of Ground Penetrating Radar Based On Compressed Sensing

The traditional GPR imaging algorithm uses the time-domain echo signal to image the underground target,its anti-noise performance is poor,and the imaging resolution is limited by the pulse width of the transmitted signal.The application of compressed sensing theory to GPR imaging can not only reduce the cost of signal acquisition,but also provide the possibility of high-resolution imaging without increasing the aperture and transmission frequency.With the progress of radar technology,MIMO radar has been applied to the underground target detection due to its many advantages such as frequency flexibility and high data acquisition efficiency.The combination of MIMO radar and compressed sensing can image the underground target with high resolution.However,when facing the underground cavity,the standard MIMO compressed sensing imaging method can not completely reconstruct the whole underground cavity.At the same time,the traditional 2D detection and imaging mode is difficult to be applied in the 3D space with unknown target position.Aiming at the three problems of pulse GPR and MIMO GPR,the work of this paper is summarized as follows:1.For the problem that the BP imaging effect is related to the pulse width and waveform of the transmitted signal and the imaging accuracy is poor,a compressed sensing convolution back projection method is proposed.Firstly,the echo signal is projected to the time-domain delay vector through compressed sensing.Then,the similarity of the two-way travel time of the nearest measuring points of the point to be imaged is used to judge whether the point is imaged or not.Finally,for the points to be imaged,the convolution sum is used to image.Experiments show that the proposed method not only has superior anti-noise performance of compressive sensing,but also has more accurate imaging.2.To solve the problem that the compressed sensing imaging of MIMO GPR can not completely reconstruct the underground cavity,a imaging method of underground cavity is proposed,which is named secondary reconstruction method.In this method,MIMO radar is used to realize fast data acquisition,and the total variation minimization algorithm is used as the reconstruction method of imaging to ensure that the imaging results have a clear edge contour.For complete imaging of the cavity,firstly,an improved histogram method is proposed to obtain the exact position of the top layer of the cavity from traditional imaging.Then,the effective array is selected by using the obtained cavities’ position information,and the cavities’ position is used as the known information to reconstruct the dictionary to solve the problem of mismatch between echo data and dictionary.Simulation results show that the secondary reconstruction method can not only image the underground cavity completely,but also has high resolution.3.Aiming at the problems that the traditional 2D imaging of GPR is difficult to use in practical operation and the imaging results are not intuitive,a 3D imaging method of multi-layer plane medium GPR based on compressed sensing is proposed.This method uses planar MIMO array to obtain detection data to improve detection efficiency.Aiming at the problems of low efficiency and inaccurate location of 2D imaging,a 3D reconstruction method of underground area using compressed sensing is proposed;Aiming at the problem that it is difficult to generalize different layered media models,a method of equivalent approximation of multi-layer media scene using equivalent media layer theory is proposed,which realizes the solution of different media layers in the same model.Experiments show that this method is intuitive and accurate in multi-layer planar media.