| dc.description.abstract | In order to understand clearly the complicated characteristics of synthetic aperture radar (SAR) especially in high-resolution condition, multi-band, fully polarization and multi-acquisition mode, more and more features need to be extracted. For recognition or identification purpose, the multi-aspect angle database is essential because of the accuracy of classification. The high angle sensitivity of SAR target image was considered. For the SAR mechanism understanding, a distinction of the backscatter electric field between each reflection and diffraction is necessary. According to the separated scattering electric field map, which reflections are due to which structures of complex target can be clearly identified. This simulator is very suitable to understand these characteristics. For the computer-aided engineering (CAE) purpose that is adopted for the engineering analysis to avoid the risk of experimentation widely, computer software orientation simulation is the earliest motivation. For the evaluation of SAR algorithm or system this simulator can be adopted to be the first version before lunching or flight-testing. For the hardware orientation emulator application, a combination of software and hardware is very suitable for providing the man-made artificial SAR complex target’s signal.
An overall simulation flowchart from simulation parameter tables to SAR target’s database was introduced in this dissertation. Different from the literature are that the interaction between target and background was considered, the purpose of this simulator was multi-angle orientation, and the optimal parallelization architecture was introduced by power of CUDA that make this simulator be authentic and usable. To implement this simulator, a lot of technologies were considered. The simulation of the back scattering electric field must consider the multi-bouncing back scattering and diffraction. For the purpose of parallelization, the ray-tracing technology was adopted. After the ray tracing, the Physical Optics (PO) and Physical Theory of Diffraction (PTD) methods with multi-layer material was adopted. For more high accuracy consideration, the Taylor expansion method was used for solving the integration of surface current. Therefore, the back scattering electric filed is not restricted in the single bounce. Furthermore, an analytical diffraction solution was adopted for the wedge structure that is very common on complex targets in CAD model especially. For reducing the computation time, a slant range sample in frequency domain was adopted to limited the number of samples in the swath region. Furthermore, the sensor path trajectory for space- and air-borne was considered. For the authenticity, bias and noise can be generated in this simulator to meet the real sensor requirement. Because that this simulator is for producing appropriate SAR databases, the SAR geometry combination with different kinds of observation type was considered such as the Circle SAR, Inverse SAR, Stripmap and Spotlight. Various SAR focusing algorithms such as the Range-Doppler Algorithm (RDA), the Omega-K Algorithm (WKA) and the Time-domain Back-Projection (TDBP) were considered too.
Base on this simulator, the heavy computation loading was profiled and figured out by a flowchart. The back scattering computation block takes a high complexity with order of cubic. The NVIDIA CUDA technology was adopted, a high speedup rate was represented in more than 200 times in the experimental dihedral results. It means that this simulator is very suitable for very complex target where number of polygon is more than one million, and for larger target that the dimension is larger than 250 by 250 meters. The computing elapsed time is almost a half hour per SAR image clip. This calculation speed makes this simulator be feasible. Finally, an MSTAR (Moving and Stationary Target Acquisition and Recognition) vehicle and larger Buckingham palace complex target models were applied to the simulator in the final chapter. The verification of target’s dimension with feature can be found those results. | en_US |