3-D Tomographic Circular SAR Imaging of Targets Using Scattering Phase Correction

Multibaseline circular synthetic aperture radar (C-SAR) tomography is an important three-dimensional (3-D) radar imaging mode since it allows for omni-directional 3-D reconstruction of targets. Typically, this imaging mode splits the full-aperture data into multiple narrow apertures to be processed separately due to the sensitivity to elevation angle and imaging height. However, the repeated one-dimensional (1-D) elevation inversion of all imaged pixels for each sub-aperture also leads to more processing time and more parameter estimation uncertainties. In this article, a new C-SAR tomography framework based on scattering phase correction (SPC) is presented. Our main idea is to use 1-D elevation inversion to estimate the exact height of the distorted scattering points in two-dimensional (2-D) full-aperture image, and derive the imaging height transformation formula. Then these distorted scattering points of different heights are transformed to the proper heights, respectively. As a result, the elevation inversion only needs to be done once for the whole framework and does not need to be done for each sub-aperture. Besides, a combination of two separate processing chains (i.e., fast coherent imaging and slices transform imaging) is used to minimize the 3-D reconstruction errors caused by the imaging height transformation and 1-D elevation inversion. Numerical and outdoor measurement results of real-world complex targets are presented to demonstrate the usefulness of the proposed framework.