Abstract
Precise azimuth-variant motion compensation (MOCO) is an essential and difficult task for high-resolution synthetic aperture radar (SAR) imagery. In conventional post-filtering approaches, residual azimuth-variant motion errors are generally compensated through a set of spatial post-filters, where the coarse-focused image is segmented into overlapped blocks concerning the azimuth-dependent residual errors. However, image domain post-filtering approaches, such as precise topography- and aperture-dependent motion compensation algorithm (PTA), have difficulty of robustness in declining, when strong motion errors are involved in the coarse-focused image. In this case, in order to capture the complete motion blurring function within each image block, both the block size and the overlapped part need necessary extension leading to degeneration of efficiency and robustness inevitably. Herein, a frequency domain fast back-projection algorithm (FDFBPA) is introduced to deal with strong azimuth-variant motion errors. FDFBPA disposes of the azimuth-variant motion errors based on a precise azimuth spectrum expression in the azimuth wavenumber domain. First, a wavenumber domain sub-aperture processing strategy is introduced to accelerate computation. After that, the azimuth wavenumber spectrum is partitioned into a set of wavenumber blocks, and each block is formed into a sub-aperture coarse resolution image via the back-projection integral. Then, the sub-aperture images are straightforwardly fused together in azimuth wavenumber domain to obtain a full resolution image. Moreover, chirp-Z transform (CZT) is also introduced to implement the sub-aperture back-projection integral, increasing the efficiency of the algorithm. By disusing the image domain post-filtering strategy, robustness of the proposed algorithm is improved. Both simulation and real-measured data experiments demonstrate the effectiveness and superiority of the proposal.
Highlights
The atmospheric turbulence disturbs the ideal trajectory of aircraft during the whole process of flight, and this causes serious blurring, and geometric distortion of the synthetic aperture radar (SAR) [1,2,3] imagery
In order to validate the theory and analysis illustrated in the previous sections, we describe an experiment performed with simulated Ka-band SAR data in this subsection
We demonstrate that the peak sidelobe ratio (PSLR) and integrated sidelobe ratio (ISLR) of PTA are both large, because necessary extension is absent in the block length and overlapping part
Summary
The atmospheric turbulence disturbs the ideal trajectory of aircraft during the whole process of flight, and this causes serious blurring, and geometric distortion of the synthetic aperture radar (SAR) [1,2,3] imagery. In PTA, the coarse-focused image is divided into overlapping sub-blocks, and the residual motion error relative to every block center is compensated for by a post-filtering strategy. Image domain post-filtering of PTA needs to segment the image into sub-blocks Because this strategy compensates the azimuth-variant motion error block-to-block, it confronts three main problems when dealing with sever motion errors. Instead of post-filtering for a sub-block in the image domain, FDFBPA compensates the residual azimuth-variant motion errors by precisely calculating the azimuth matched filtering (AMF) [15] function, and using the fast back-projection process in the azimuth wavenumber domain. 2 gives fully the geometry modelwith and high calculates the for the PTA, FDFBPA focused images efficiency precise expression of signal with residual azimuth-variant motion error in azimuth wavenumber and robustness, and is suitable for real airborne SAR imagery. Illustrated in detail; Section 4 shows a flowchart of the proposed FDFBPA and analyzes computation burden; in Section 5, extensive experimental results with both simulated and real Ka-band airborne
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
