Research On Key Technologies Of Ground-based Synthetic Aperture Micro Deformation Monitoring Radar

In recent years,more and more large-scale buildings,such as the construction of highrise buildings in urban areas,the construction of various bridges,the construction of reservoir dams and so on,have brought great convenience to our life.At the same time,it is of great practical significance to carry out the comprehensive safety monitoring of buildings,which is related to the safety of everyone's life and property,and to ensure the normal operation of these buildings.Therefore,ground-based synthetic aperture radar(GB-SAR),a new deformation monitoring method,has become a research hotspot,and this paper has also carried out research on it.GB-SAR system can monitor the target area 24 hours a day,without contact.At present,there are two problems in the process of GB-SAR measuring target deformation.Firstly,the deformation information beyond the line of sight can not be obtained,even if the two-dimensional information can be obtained,the real deformation information of the target can not be obtained;secondly,when monitoring and extracting the permanent scatterer from the target area,the traditional method ignores the feature of high SNR of the target,and it is easy to be affected by the adjacent pixels,resulting in the decrease of the accuracy of the result.The main contents and achievements of this paper are as follows:(1)Aiming at the problem that the traditional GB-SAR can only monitor the onedimensional line of sight displacement of the target,a parallel synthetic aperture radar fusion multi aperture interference technology is proposed to obtain the three-dimensional displacement of the target.Firstly,the target area is monitored by the main synthetic aperture radar,and the two-dimensional displacement of the target is obtained by using the multi aperture interference technology.Then,the parallel synthetic aperture radar is arranged to monitor the displacement of the target area in another direction.The spatial rectangular coordinate system is established,and the position relationship of each deformation vector is analyzed.Through a series of logical operations,the displacement of the target in the third dimension can be obtained.Finally,the MATLAB software is used to simulate the threedimensional deformation analysis process.The results show that this method can get the accurate three-dimensional deformation size of the target and the error is in the sub millimeter level.(2)In order to meet the requirement of real-time and high precision in the processing of GBSAR deformation monitoring technology,in this paper,the traditional selection method of permanent scatterer(PS)is added to the real-time empirical mode decomposition method,which can accurately screen out PS points with high signal-to-noise ratio.The whole process is divided into two steps.Firstly,most of the weak scatterers can be removed by the traditional PS point recognition method-amplitude dispersion threshold method.Then,with the help of phase dispersion threshold method,the candidate PS point set can be obtained.In the second step,empirical mode decomposition method is used to decompose the time series of candidate PS points one by one,set a certain threshold,and select the scatterer with high signal-to-noise ratio as the permanent scatterer.This method is simple in data processing and does not depend on the scattering characteristics of the surrounding scatterers.It can avoid some false and missed selections and find permanent scatterers with high SNR.