Research On Imaging And Motion Compensation Method Of Circular SAR

Circular SAR(CSAR) is a new type of three-dimensional synthetic aperture radar imaging mode, it can all- day all-weather 360 degree 3D imaging on target, and it has extensive application prospects in the fields of military reconnaissance, topographic mapping and security inspection and so on. In this thesis, we study the problem of the imaging algorithm and motion compensation method of circular SAR system. The main research contents and contributions of this thesis are as follows:1. This thesis firstly introduces the basic principle of circular SAR imaging system, include: echo model in the time domain and frequency domain of the circular SAR under the far-field plane wave assumption, three dimensional resolution formula of circular SAR. Then, this chapter introduces the commonly used circular SAR imaging algorithm: the wave number domain imaging algorithm and the back projection algorithm. Finally, the back projection autofocus algorithm is introduced.2. A 3D imaging algorithm of circular SAR based on dimension reconstruction is studied. This algorithm combines the idea of fractal dimension reconstruction with the orthogonal matching pursuit algorithm(OMP), lastly the reconstructed results of each dimension are reconstructed and the results are obtained. The advantages of the algorithm are verified by simulated data and measured data. Compared with the 3D back projection imaging algorithm, the imaging results of the method have higher resolution and practical application has advantages.3. Three dimensional fast imaging algorithm of circle SAR is studied. A method of parallel implementation of 2D back projection algorithm based on GPU is introduced and the algorithm is extended to 3D. A three dimensional fast back projection image algorithm based on GPU for circular SAR is proposed, this algorithm combines the principle of GPU parallelization with the back projection algorithm. The advantages of the algorithm are verified by simulated data and measured data. Compared with the traditional CPU back projection algorithm, this method greatly improves the efficiency of the 3D image of the circular SAR system and practical application has advantages.4. A multiple-subapertures autofocusing algorithm for circular SAR imaging is proposed, this method combins the sub aperture technique with the back projection autofocusing algorithm. The influence of the change of the radar scattering coefficient(RCS) with the angle of view angle on the circular SAR back projection autofocusing algorithm imaging resolution low is overcome. The advantages of the algorithm are verified by simulated data and measured data. Compared with the original cirular SAR back projection autofocus algorithm, this algorithm can effectively image the circular SAR data and practical application has advantages.5. A sub-image synthesis autofocusing algorithm based on minimum entropy is proposed. This algorithm combines the sub-image synthesis technology with the minimum entropy autofocusing algorithm, this algorithm can focus circular SAR image when image has not strong scattering point. The advantages of the algorithm are verified by simulated data and measured data.