Based On The Near Space Platform Of Surveying And Mapping With High Resolution Wide Research On Sar Imaging Algorithm

Synthetic Aperture Radar (SAR) can do detections to a region all day, all the time, all-weather and also with long distance. High resolution and wide swath radar is one of the most important research direction of synthetic aperture radar. Wide swath can be used to complete global monitoring in a short time and monitor a particular area repeatedly. For the conventional SAR, width swath range and high resolution azimuth are contradictions because of the limitations of minimum antenna area. As the traditional SAR is a single input and single output (SISO) system, it is able to reduce the required pulse repetition frequency (PRF) of system by increasing the number of equivalent phase center. With the development of beamforming and signal processing, there have been numerous literatures discussing single input multiple output (SIMO) SAR system, Thiseven more multiple input output(MIMO) SAR aystem. This thesis starts from the contradictions of high resolution and wide swath, discusses a new field of space named near-space by which to realize these two goals with more advantages than space borne and airborne. Near-space is the airspace which is20km to100km away from ground. This airspace is neither the scope of aerospace nor the scope of aviation. Near space vehicle has many advantages such as high price ratio, high mobility, strong viability, as well as staying at the same location with long time.This thesis builds a SAR system based on near-space platform. Firstly, the principle of SCAN SAR imaging algorithm is described. Secondly, system parameter design and echo model are build. Then, imaging simulations based on SPECAN algorithm are done. This thesis prompts a good algorithm named SPECAN to solve fan distortion which is caused by the variable sampling interval. SCAN SAR can realize wide swath, but with the cost of the expense of azimuth resolution. SCAN SAR obtains wide swath by range scan. With the inspiration of that, this thesis proposes a new SAR algorithm by which can realize range multi-aperture receiver with both high resolution and wide swath. Then, this thesis detailed describes its working principle, echo model building and system parameter design. Finally, the imaging results of simulation are showed. It is a multiple input single output system, which reduces the PRF of system by increasing the number of range equivalent phase center. As received signals include the phase information of the target points of each sub-swath which relative to each sub-aperture, this thesis uses these phase information to build an anti-solution matrix, and then uses anti-solution matrix to restore echo signals superimposed by multiple sub-swath to their correct positions. To restore the correct signals, the pathological of anti-solution matrix is a key point. This thesis analyses the pathological of anti-solution matrix in detail, and then does the performance analysis to the simulation results.