Research On SAR Imaging Method Of Shallow Underground Targets

The detection of shallow underground targets is mainly to obtain the information about the position,scattering intensity,shape and size of the target through the characteristics of electromagnetic wave transmission in non-uniform media and its reflection and refraction.The imaging results are important for target detection and recognition Guiding significance.Synthetic aperture radar(Synthetic Aperture Radar,SAR)imaging methods are relatively mature,but they are all based on a uniform medium model,suitable for imaging processing of ground targets.The model has more in-depth research.Therefore,this paper studies the imaging model of non-uniform media on the basis of the uniform media model,which can make the target have accurate positioning.In order to further focus the target better,this paper studies four methods of side lobe suppression,and proposes a method of side lobe suppression based on sub-aperture according to the principle of sub-aperture superposition of backward projection algorithm.The imaging models have good side lobe suppression effect.The main work of this article is as follows:This article first gives a brief overview of the four types of algorithms for synthetic aperture imaging,and highlights the backward projection algorithm suitable for near-field imaging.The research status of the backward projection algorithm for underground targets and its side lobe suppression The situation has been elaborated,pointing out the necessity for non-uniform medium model imaging and its sidelobe suppression research.Then,based on the imaging principle of the backward projection algorithm,the point target was simulated,and the effects of the radar azimuth scanning interval and dielectric constant on the imaging effect were analyzed.Then,for the backward projection algorithm imaging The side lobe problem was studied,and four different side lobe suppression methods,including window processing,ramp function filtering,spatial apodization filtering,and variable aperture weighted window function,were studied in depth.These four methods were used in the side lobe of imaging results.In the processing,the suppression effect is compared and the performance is evaluated.Finally,a set of experimental data is used to suppress the side lobe,which is consistent with the simulation effect.Finally,based on the imaging of the uniform medium model,the imaging model of the target in the non-uniform medium is studied and derived,and the correctness of the model is verified by the simulation results.Aiming at the side lobe problem in imaging results,a sub-aperture-based side lobe suppression method is proposed based on the principle of sub-aperture superimposed imaging based on the backward projection algorithm.Through the processing of simulated data and measured data,the method is verified in a non-uniform medium model It has a good ability to suppress non-orthogonal side lobes.Comparison with the processing results of other side lobe suppression methods proves that this method has better side lobe suppression effect.