Study Of Motion Compensation Algorithm Of SAR Imaging Based On Platform’s Complex Movement

The research on SAR imaging algorithm under the condition of radar platform’s complex trajectory needs development in order to accommodate the engineering application of all kinds of motion platform which are used to carry synthetic aperture radars and make sure that the performance of the algorithm will not be affected by the influence of motion error factors, for example:airstream, gravitational force, mechanical operation, etc. The present thesis is focus on the SAR motion compensation imaging algorithm under the condition of SAR’s complex movement, have analyzed the modeling of several complex movement trails, the threshold of motion parameters when the motion trail can no longer be used to SAR imaging and the motion compensation algorithms focus on the complex trajectory. The main research can be divided into several parts as follows:In the first place, the present thesis have made flying modeling of various flying mode based on the research of the complex motion trajectory in order to get the modeling of the instantaneous distance between radar and the target under the different flying modes. This shows that the parameters like effective time of synthetic aperture and frequency bandwidth will be affected seriously under the complex movements, so that the images’ resolution will degrade or even can’t get an image if only using the traditional imaging algorithm. In this thesis the motion error threshold of different motion types is also analyzed in details.In the second place, the present thesis shows the motion errors’impacts on space-variance characteristic of parameters in the form of diagram, and also shows the phase errors’ impacts on motion compensation algorithm. By the analysis of statistic experiments, the traditional strict error threshold is widened and a new phase error threshold is defined based on those experiments, which is when the sampling amounts when the phase error is bigger than π/4 is smaller than 30 percent of whole sampling amounts in the time of synthesis aperture, the impact of the phase error to the imaging quality can be ignored.Last but not the least, the present thesis put great emphasis on the two-dimension frequency spectrum’s high order expression based on the research of the modeling of the instantaneous distance between radar and the target when the radar’s movement is complex, which is get by using of the Fourier Transform and Principle of Stationary Phase, thus get the great difference of SAR echo signal’s characteristic between the complex motion and the ideal motion which is uniform rectilinear motion. Also the present thesis have do some research on the motion compensation algorithm of the SAR imaging under the condition of the complex motion. Start with the high order two-dimensional spectrum, based on the impact of complex motion on the SAR echo signal’s characteristic, block compensation algorithm under the consideration of both phase compensation and the space-variance characteristic is analyzed in details. And the simulation of the proposed motion compensation algorithm has proved that the algorithm is reliable and effective for SAR motion compensation under the condition of the complex motion.