Improved Pencil Back-Projection Method with Image Segmentation for Far-Field/Near-Field SAR Imaging and RCS Extraction

In order to alleviate the far-field requirement from RCS measurements, a two-step procedure of first obtaining the SAR image of the object followed by an RCS extraction has been recently introduced. In this manuscript, a spotlight mode SAR-imaging algorithm that improves far-field and near-field tomographic reconstruction resolution (and RCS extraction accuracy) is presented. This algorithm comprises the following steps: 1) the range profiles are obtained with super resolution by utilizing the band-pass matrix pencil method. 2) Back-projection, which does not require polar-to-Cartesian interpolation in the spectral domain, is used for the far-field or near-field image reconstruction. 3) Background of the reconstructed image is removed with the Otsu´s thresholding. 4) Complex amplitudes and locations of the scattering centers are selected from the thresholded image with an amplitude extraction procedure. Finally, obtained scattering centers are used for RCS extraction. The simulation and measurement results show that the unfavorable effects of the point spread function are reduced with the developed algorithm, and hence, the quality of the SAR image is increased, and the accuracy of the extracted RCS is improved.