Fourier reconstruction in spotlight mode SAR imaging

Abstract

The spotlight mode SAR imaging procedure can be modeled in two ways. One is from the projectional information introduced from computer-aided tomography (CAT) founded on the projection-slice theorem. By quoting the concept "projection" from CAT to microwave imaging, the spotlight mode SAR can be interpreted as a narrow band tomography reconstruction problem in the far field and small rotation angle situation. Another kind of modeling in the spotlight mode SAR comes from the conventional stripmap SAR directly, in which the processed echo returns are verified to have the same Fourier information as that in the first way. From these two points of view, the spotlight mode SAR can be unified to the problem of Fourier reconstruction (FR). A common problem motion through resolution cells (MTRC) caused by relative rotation in spotlight SAR is characterized as a main factor in imaging smearing or defocusing. Data polar formatting is adopted as an effective solution either of data reconstruction or phase focusing.