Research On Ground-Based SFCW SAR Differential Interferometry Techniques

The ground-based stepped frequency continuous wave synthetic aperture radar differential interferometry technique can achieve an accuracy of sub-millimeter. It has the ability of real-time monitoring a remote and large-scale area, and covering a continuous space. The technique has been widely used in monitoring man-made structures and the earth's surface deformation field. In this thesis, based on ground-based SFCW SAR system observation model and differential interferometry data processing, some critical techniques about the ground-based SFCW SAR differential interferometry are studied focusing on how to improve the system measurement accuracy. The work can be summed up as the following four parts:Firstly, the ground-based SFCW SAR system observation model is established, and then analyzed stepped frequency continuous wave range synthesis and azimuth synthetic aperture imaging. The major factors which influence the accuracy of ground-based SFCW SAR differential interferometry measurement are observation platform instability, system frequency instability, differential phase error, and actual displacement error due to calculate. Simulation tests on these factors are conducted.Secondly, two critical techniques of the ground-based SFCW SAR differential interferometry, which are the registration of sub-pixel GB-SAR complex image and atmospheric disturbance effect correction, are studied. An algorithm for GB-SAR complex image co-registration was adopted based on Fourier-Mellin transformation and Correlation-Coefficient , and experiments are implemented to verify that the co-registration accuracy of this algorithm attains sub-pixel level. In terms of atmospheric disturbance, an experiment is designed to analyze and correct its effect. In this experiment, atmospheric disturbance effect is corrected by the man-made control points method and the compensation algorithm based on meteorological parameters. Measurement accuracy of SFCW SAR differential interferometry is improved as experiment results show.And then, a displacement measure experiment for differential interferometry is carried out by using ground-based SFCW SAR system. Experiment results show that measurement accuracy can reach sub-millimeter. It demonstrated that the system has high stability, and can dynamic monitor object deformation with high accuracy.Finally, the ground-based SFCW SAR differential interferometry techniques is applied to through-the-wall motion detection, and a new motion detection method was proposed. Compared with traditional no-coherent change detection method, further interferometry phase detection is added to the new method. Experimental results show that the new approach can reduce false alarms effectively under the same detection probability.