Refocusing and Zoom-In Polar Format Algorithm for Curvilinear Spotlight SAR Imaging on Arbitrary Region of Interest

For conventional polar format algorithm (PFA), because of the image distortion and defocus caused by the plane-wave assumption, the effective imaging scene is bounded to a small region near the reference point. In this paper, refocusing and zoom-in polar format algorithms (RZPFAs) for curvilinear spotlight synthetic aperture radar (SAR) imaging are proposed, which can produce refocused image for an arbitrary region of interest (ROI). First, refocusing is implemented by a phase compensation of the already dechirped signal with respect to the new refocusing point. The relation [named refocused distortion mapping (RDM)] between targets’ actual locations and their reconstructed locations in the refocused image is then derived. Based on the RDM, the distortion-negligible region (DiR) and defocus-negligible region (DeR) are defined as extents within which the residual distortion and residual defocus are less than some preselected thresholds. When the ROI is within both the DiR and the DeR, zoom-in imaging based on nonuniform fast Fourier transform of type-1 (NuFFT-1) is sufficient to form a desired image, which is named RZPFA based on NuFFT-1 (RZPFA-1). However, when the ROI exceeds the DiR, zoom-in imaging based on nonuniform fast Fourier transform of type-3 (NuFFT-3) should be selected, which is named RZPFA based on NuFFT-3 (RZPFA-3). With just a small amount of extra computation than RZPFA-1, RZPFA-3 can realize pixel-based quasi-orthorectified imaging directly. Besides, the proposed algorithms can also be extended to wide-area persistent imaging where ROI is larger than DeR. The simulation and real data results demonstrate the effectiveness of the proposed algorithms.

[1]  L. Greengard,et al.  The type 3 nonuniform FFT and its applications June - , 2005 .

[2]  Jack Walker,et al.  Range-Doppler Imaging of Rotating Objects , 1980, IEEE Transactions on Aerospace and Electronic Systems.

[3]  Giovanni Toso,et al.  Fast, Phase-Only Synthesis of Aperiodic Reflectarrays Using NUFFTs and CUDA , 2016 .

[4]  Yiming Pi,et al.  A Video-SAR Imaging Technique for Aspect-Dependent Scattering in Wide Angle , 2017, IEEE Sensors Journal.

[5]  Lars M. H. Ulander,et al.  Synthetic-aperture radar processing using fast factorized back-projection , 2003 .

[6]  F. Rocca,et al.  SAR data focusing using seismic migration techniques , 1991 .

[7]  Amedeo Capozzoli,et al.  The 2D Type-3 Non-Uniform FFT in CUDA , 2018 .

[8]  Daiyin Zhu,et al.  Range Resampling in the Polar Format Algorithm for Spotlight SAR Image Formation Using the Chirp $z$ -Transform , 2007, IEEE Transactions on Signal Processing.

[9]  Yihui Lu,et al.  A new subaperture approach to high squint SAR processing , 2001, IEEE Trans. Geosci. Remote. Sens..

[10]  Feng Zuo,et al.  An algorithm for persistent imaging of curvilinear video SAR , 2018, 2018 IEEE Radar Conference (RadarConf18).

[11]  Jianyu Yang,et al.  SAR Automatic Target Recognition Based on Multiview Deep Learning Framework , 2018, IEEE Transactions on Geoscience and Remote Sensing.

[12]  Brian D. Rigling,et al.  New Phase Error Corrections for PFA with Squinted SAR , 2017, IEEE Transactions on Aerospace and Electronic Systems.

[13]  Xinhua Mao,et al.  Polar format algorithm wavefront curvature compensation under arbitrary radar flight path , 2011 .

[14]  Gabriele Steidl,et al.  Fast Fourier Transforms for Nonequispaced Data: A Tutorial , 2001 .

[15]  L. Greengard,et al.  Short Note: The type 3 nonuniform FFT and its applications , 2005 .

[16]  Robert Hawley,et al.  Wide-area, persistent SAR imaging: Algorithm tradeoffs , 2014, IEEE Aerospace and Electronic Systems Magazine.

[17]  Neeraj Magotra,et al.  Space-variant post-filtering for wavefront curvature correction in polar-formatted spotlight-mode sar imagery , 1999 .

[18]  Yingning Peng,et al.  Feature-Independent Aperture Evaluator for the Curvilinear SAR , 2007, IEEE Geoscience and Remote Sensing Letters.

[19]  Daoxiang An,et al.  Extended Nonlinear Chirp Scaling Algorithm for High-Resolution Highly Squint SAR Data Focusing , 2012, IEEE Transactions on Geoscience and Remote Sensing.

[20]  R. Keith Raney,et al.  Precision SAR processing using chirp scaling , 1994, IEEE Trans. Geosci. Remote. Sens..

[21]  Hongqiang Wang,et al.  An Improved PFA With Aperture Accommodation for Widefield Spotlight SAR Imaging , 2015, IEEE Geoscience and Remote Sensing Letters.

[22]  Leslie Greengard,et al.  Accelerating the Nonuniform Fast Fourier Transform , 2004, SIAM Rev..

[23]  Mehrdad Soumekh Time Domain Non-Linear SAR Processing , 2006 .

[24]  A. F. Yegulalp Fast backprojection algorithm for synthetic aperture radar , 1999, Proceedings of the 1999 IEEE Radar Conference. Radar into the Next Millennium (Cat. No.99CH36249).

[25]  Charles V. Jakowatz,et al.  Space-variant filtering for correction of wavefront curvature effects in spotlight-mode SAR imagery formed via polar formatting , 1997, Defense, Security, and Sensing.

[26]  Armin W. Doerry,et al.  An efficient means to mitigate wavefront curvature effects in polar format processed SAR imagery , 2012, Defense + Commercial Sensing.

[27]  Kenneth Knaell,et al.  Three-dimensional SAR from curvilinear apertures , 1994, Proceedings of the 1996 IEEE National Radar Conference.

[28]  Feng Zuo,et al.  Improved Method of Video Synthetic Aperture Radar Imaging Algorithm , 2019, IEEE Geoscience and Remote Sensing Letters.

[29]  Michael T. Orchard,et al.  A fast direct Fourier-based algorithm for subpixel registration of images , 2001, IEEE Trans. Geosci. Remote. Sens..

[30]  Brian D. Rigling,et al.  Fast corrections for polar format algorithm with a curved flight path , 2016, IEEE Transactions on Aerospace and Electronic Systems.

[31]  Brian D. Rigling,et al.  Scene size limits for polar format algorithm , 2016, IEEE Transactions on Aerospace and Electronic Systems.

[32]  Christophe Magnard,et al.  Focusing of Airborne Synthetic Aperture Radar Data From Highly Nonlinear Flight Tracks , 2009, IEEE Transactions on Geoscience and Remote Sensing.

[33]  Gordon Davidson,et al.  A new approach to coherent change detection in VideoSAR imagery using stack averaged coherence , 2013, 2013 IEEE Radar Conference (RadarCon13).

[34]  Isaac Amidror,et al.  Scattered data interpolation methods for electronic imaging systems: a survey , 2002, J. Electronic Imaging.