Research On Micro-Deformation Monitoring Technology Based On FMCW GBSAR

Faced with problems of traditional micro-deformation monitoring methods,such as high hardware cost,low efficiency and dangerous in application regions,new micro-deformation monitoring equipment(ground-based synthetic aperture radar,GBSAR)is designed based on frequency modulated continuous wave,synthetic aperture radar imaging technology and phase retrieve technology to acquire micro-deformation.The device is capable of monitoring regions which are several kilometers away.It can acquire micro-deformation in sub-millimeter level with surface monitoring ability for regions at a long distance.This provides a new method for monitoring and alarming for geological disasters such as landslides and earthquakes.In addition,it can be used in monitoring and alarming for accident caused by old buildings or damaged buildings.Conventional deformation monitoring methods cannot be used in some regions such as mountains and glaciers,because they require a large number of displacement sensors or GPS transceivers to be installed closely with the monitoring region.To solve this problem,GBSAR is used in such regions where is complex in geography and inconvenient to arrive.This is realized by the GBSAR system which is portable with a low weight.By using frequency modulated continuous wideband wave,the GBSAR prototype designed in the paper is less in weight with an integrated signal transceiver which is only 3.5Kg.In addition,it can be used in regions where are far away by the system's wide cover length in kilometers level.The major works and originalities in this dissertation are as follows:(1)Micro-deformation monitoring method is studied based on the principle of micro-deformation monitoring by GBSAR.Faced with problems of traditional micro-deformation measure methods,a micro-deformation measure method based on millimeter-wave ground-based synthetic aperture radar is proposed in the paper.And,a GBSAR prototype is designed.Based on the observation model of GBSAR,relationship between the target's micro deformation and the radar echo's phase is acquired.Therefore,method to acquire the target's micro-deformation from the radar echo by phase retrieve is proposed.This method improves the precision of the micro-deformation monitoring.And,the GBSAR's micro-deformation measure precision can be in sub-millimeter level,which is higher than the precision acquired by spacebrone interferometric synthetic aperture radar.(2)Normally,all echoes in one aperture's length along the azimuth direction cannot be obtained by the GBSAR which is constrained by the real length of the rail guide which is the carrier platform for the GBSAR system.Faced with this problem,imaging capability and micro deformation monitoring capability of the GBSAR system are studied.Through simulation by Matlab/SIMULINK,target imaging and deformation measure ability of the system are verified.Experiment results show that the system has a high imaging resolution.At the same time,interferogram is obtained based on two radar images of the same area at different times.Thus,it is validated that the system can acquire the micro deformation of the target by phase retrieving.(3)In general,monitoring regions are complex in geography and harsh in environment.An integrated microwave signal transceiver based on the frequency-modulated continuous wave is proposed in the paper to make the radar system weight less.The radar prototype is flexible and can be operated easily.Thus,it can be used in some micro-deformation monitoring regions such as mountains and valleys.Meanwhile,an uninterruptible power supply system is integrated in the radar prototype to solve the problem of lacking power in mountainous area.In addition,waveguide slot array antennas are designed in the system.It improves the imaging capability of the system.(4)GBSAR's monitoring ability for micro-deformation in one dimension is studied.Micro-deformation monitor method in real aperture mode is proposed to been used in bridge's vibration monitoring applications,to solve the problem of bridge's vibration which is fast in velocity and small in amplitude.Through experiments in typical buildings such as light railway bridge,high-speed railway bridge and large suspension bridge,the effectiveness of the system in micro-deformation monitoring is validated.This monitoring method can avoid the defects of traditional micro-deformation monitoring method by removing tedious work in sensor installation.It also improves the monitoring efficiency,meeting the requirements of timeliness in the deformation monitoring process.(5)Faced with the problem of complex and changeable characters of monitoring regions in natural environment,micro deformation monitoring ability of the GBSAR system in two dimensions is studied.The measure ability of the radar prototype system to measure the permanent scatter's deformation is verified based on the permanent scatter technology.Experiment results show that the radar prototype system is effective in monitoring the micro deformation of the natural region.Thus,it lays a foundation for the subsequent research work.Finally,the paper summarizes the work done in the paper and analyses the prospect of the radar in the future.