An Autofocus Cartesian Factorized Backprojection Algorithm for Spotlight Synthetic Aperture Radar Imaging

• Published in: IEEE geoscience and remote sensing letters Vol. 15; no. 8; pp. 1244 - 1248
• Main Authors: Luo, Yin, Zhao, Fengjun, Li, Ning, Zhang, Heng
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 01.08.2018; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Algorithms; Apertures; Autofocus; Azimuth; backprojection (BP); Cartesian coordinates; Cartesian factorized BP (CFBP); Compression; Error compensation; Fourier transforms; History; Image coding; Imaging; Imaging techniques; Mathematical models; Methods; Performance enhancement; Phase error; Radar; Radar imaging; Radar polarimetry; SAR (radar); Singular value decomposition; Synthetic aperture radar; synthetic aperture radar (SAR)
• ISSN: 1545-598X; 1558-0571
• DOI: 10.1109/LGRS.2018.2829483

A backprojection (BP) algorithm is recognized as an ideal method for high-resolution synthetic aperture radar (SAR) imaging. Several fast BP algorithms have been developed to enhance the efficiency of the BP integral. The Cartesian factorized BP (CFBP) algorithm is proposed recently to avoid massive interpolations and improve the performance. However, integrating autofocus techniques with the CFBP has not been discussed. In this letter, an autofocus CFBP algorithm is proposed to compatibly combine the autofocus processing within the CFBP. After modifying the spectrum compression step in the CFBP, the approximate Fourier transformation (FT) relationship between the modified compensated subaperture images and the corresponding range-compressed phase history data in the Cartesian coordinate is revealed. The phase error is obtained by the multiple aperture map drift method, and the singular value decomposition total least square method is combined to improve the estimate robustness. Employing the range blocking method, the range variance of the phase error is compensated. The proposed algorithm inherits the advantages of the CFBP. Experiments performed by the X-band airborne SAR system with a maximum bandwidth of 1.2 GHz validate the proposed approaches.