SAR Imaging And Trajectory Calculation Of Motion Target

Synthetic Aperture Radar (SAR) is full-climate, full-time and high-resolution imaging radar. It could provide two dimension image of a region and detect the specific target. However, traditional SAR could only generate the image of static target. If the target is moving, the corresponding image will have smear in the azimuth direction and the target will be unfocused, which will construct an incorrect image of the motion target.However, there is strong need of imaging the motion target by SAR. Take the sea vessel as an example, if the image of vessel could be reconstructed, then further research could be processed such as trajectory calculation and position estimation, which is widely used in military tasks. As for the non-military use, image of motion target could also be applied for monitoring and controlling of vessels. Therefore, this thesis did some research of motion target SAR imaging and trajectory calculation.First of all, the signal model is built and analyzed to establish the mathematics equation of Doppler centroid and Doppler rate caused by target motion. Related impacts on image by using tradional SAR are also analyzed.Then clutter lock and auto focus methods are proposed to estimate the Doppler centroid and Doppler rate of the motion target, known as nominal envelop algorithm and minimum entropy filter. Use nominal envelop of signal's power spectrum as a correlation function to search the Doppler centroid. Use entropy as a criterion of image quality to search the Doppler rate adaptively by minimizing the entropy of image. A novel algorithm is used to find the Doppler rate, called adaptive step forward searching algorithm. Lots of simulation is done to verify the algorithms.Finally, both velocities in range direction and azimuth direction of the motion target are estimated. A series test of different velocities is done and the result is shown.