Algorithms For Spotlight Mode SAR Image Formation Based On Along-Track Alignment And Format System

The spotlight mode SAR, which can obtain extremely fine azimuth resolution, is an important imaging mode of SAR. However, the MTRC soars severely with wider azimuth angular interval and finer resolution, which causes distortion and defocusing in SAR image that limit useful scene size. Data formatting is a critical element in a fine-resolution SAR image formation processor. In this dissertation, the presence of range curvature distortion in conventional PFA is analyzed from data format perspective. RMA,another common choice for producing fine resolution imagery in spotlight mode besides PFA, is potentially the ideal algorithm for fine-resolution SAR imaging of large scenes, because it does not suffer range curvature distortion. A disadvantage of the RMA is that the RMA must operate on azimuth chirped signal data, which leads to an unnecessarily high along-track sampling rate for SAR system.WPFA, SPA, DDA and RSP are four novel algorithms, which use the Along-Track Alignment and Format System (ATAFS) in conjunction with conventional data processing stages. ATAFS introduces a spatially-variant modification of the SAR phase history storage format, which enable full image quality over large scenes without range curvature distortion or image defocus. WPFA, SPA and DDA, which avoid range curvature distortion using ATAFS and coordinate transformation, complete the MTRC correction. These three algorithms process data into the ideal format, with the potential for fine-resolution SAR imaging of large scenes. Requiring no interpolation, RSP has a computational burden compatible with real-time survey or field processing. To be more efficient and less storage, the reference function of ATAFS is modified in order to operate on data stabilized to a fixed reference point, and the data is resampled at lower azimuth sample rate, which are presented in this dissertation. Furthermore, WPFA is applied to the real data case and data processing result is provided.