J4 ›› 2014, Vol. 41 ›› Issue (3): 26-32.doi: 10.3969/j.issn.1001-2400.2014.03.005

• Original Articles • Previous Articles     Next Articles

Phase gradient autofocus within FFBP flow for spotlight SAR processing

LI Haolin;CHEN Lulu;ZHANG Lei;XING Mengdao;BAO Zheng   

  1. (National Key Lab. of Radar Signal Processing, Xidian Univ., Xi'an  710071, China)
  • Received:2013-06-07 Online:2014-06-20 Published:2014-07-10
  • Contact: LI Haolin E-mail:lihaolin322@163.com

Abstract:

Fast Factorized Back-Projection (FFBP) is an effective algorithm constructed based on aperture factorization. It is shown that the image quality is barely sacrificed compared with Back-Projection (BP). Different from frequency domain algorithms, SAR images reconstructed by FFBP cannot satisfy the requirement of autofocus. To solve this problem, we propose an improved FFBP (IFFBP) by introducing a fire-new coordinate system in this paper. Then, IFFBP can provide autofocus with Fourier transform pairs (FTP) between the image domain and the range compressed phase history domain. With a different framework of the overlapped subaperture in different stages, phase gradient autofocus (PGA) can be embedded into IFFBP to obtain a robust estimation of the phase error. Finally, the processed results of the collected data set validate this approach in spotlight SAR imagery.

Key words: fast factorized back-projection (IFFBP), pseudopolar coordinates, Fourier transform pairs, phase gradient autofocus, motion compensation