Research On Underground Target Imaging Technology Based On Polarization Frequency Diversity Array Radar

With the rapid development of industry,the problems of groundwater pollution as well as roadbed settlement and water accumulation are becoming more and more serious.Carrying out research on ground physical detection technology is of great significance to protect people's life and property safety and promote green ecological development and social harmony and stability.Due to the complexity of the underground detection environment and the limitations of the target information acquisition and data processing methods,the inherent defects of traditional ultra wideband ground penetrating radar can not be ignored.For example,the dispersion effect of the ultra-wideband signal caused by the subsurface consumable medium makes the existing GPR technology cannot effectively infer the location and direction of the fissure and other information.Therefore,this paper adopts the idea of multi-diversity,combining the frequency diversity array and polarization diversity technology,and conducts research on the buried target body imaging technology and direction estimation in the subsurface medium,and the main research contents are as follows:1.The basic theory of ground-penetrating radar is introduced.The dispersion phenomenon of ultra-wideband signals in a dissipative medium is analyzed.The basic theory of frequency diversity array is introduced,the corresponding subsurface target detection model is constructed,the corresponding simulation of the constructed model is carried out by using gpr Max3 D and FEKO electromagnetic simulation software,and the data processing of the simulation results is carried out by using Matlab software.2.An improved back projection algorithm is proposed.Aiming at the problem of high side lobes in the traditional back projection algorithm,effective array elements are divided for different points to be imaged,and the correlation between the echoes of each array element is used.It is improved,and the results show that the improved algorithm can effectively suppress the sidelobes.Aiming at the problem of media parameter estimation around slender buried targets,a media parameter estimation method based on image entropy is proposed.The characteristic parameters of the medium have a great influence on the propagation speed of electromagnetic waves.For the same area to be imaged that contains the target,when the area is imaged with different dielectric characteristic parameters,the imaging results obtained are different.The smaller the entropy value of the imaging result,the better the imaging focus when using this parameter,and the closer the corresponding medium parameter is to its true value.Then the relevant factors affecting the estimated value of the medium are analyzed.Experimental results show that when the target is a slender target body,the proposed parameter estimation method can effectively estimate the medium surrounding the target body.3.A method for estimating the direction of a slender buried target is proposed,which uses polarization information to estimate the direction of the underground target.The changes of the polarization scattering matrix under different angles between the cylindrical target and the array are analyzed,and the estimated value of the angle between the target and the array is expressed according to the changes of elements in the scattering matrix.Imaging the target data at different angles can get different target characteristics.Combined with the angle estimation method,it can make a more effective estimation of the target direction;for different polarization information reflecting the characteristics of different aspects of the target,adopt The polarization fusion method combines the common polarization component and the cross polarization component to reflect the different characteristics of the target.The experimental results show that the fusion imaging results basically retain the target in the common polarization mode and the cross polarization mode.The original features under.