Abstract
Multichannel signal processing in azimuth is a vital technique to enable a wide-swath Synthetic Aperture Radar (SAR) with high azimuth resolution. However, the multichannel high-resolution and wide-swath (HRWS) SAR system always suffers from the problem of the azimuth nonuniform sampling resulting in the image ambiguity, when it does not satisfy the uniform sampling condition. In this paper, to suppress the azimuth image ambiguity, we propose a novel unambiguous reconstruction method based on image fusion. During this reconstruction processing, the Back Projection (BP) algorithm is first utilized for SAR imaging to obtain the designed sub-images. Then, the reconstruction expression is derived as the summation of the sub-images weighted by the interpolation coefficient. This method integrates the reconstruction into the imaging process and the image fusion makes the procedure simple. In addition, the interpolation period, which affects the reconstruction image quality and efficiency, is further analyzed. Moreover, as the curved trajectory platform brings more challenges for the unambiguous reconstruction, the performance of the proposed method applied to the curved trajectory platform is studied. Finally, experimental results clearly verify the effectiveness of the proposed method for ambiguity suppression and demonstrate its applicability to the curved trajectory.
Highlights
With the further research on the Synthetic Aperture Radar (SAR) imaging technology, high resolution and wide swath (HRWS) imaging has become an important trend for the future Earth observation [1]–[4]
The effective phase centers (EPCs) of the multichannel SAR system will always be nonuniformly distributed in azimuth, shown in Fig.2, which results in periodic nonuniform sampling in azimuth
To solve the problem of unambiguous reconstruction, the proposed image domain reconstruction (IDR) approach is applied to the multichannel nonuniform sampling data
Summary
With the further research on the Synthetic Aperture Radar (SAR) imaging technology, high resolution and wide swath (HRWS) imaging has become an important trend for the future Earth observation [1]–[4]. To increase the robustness of the reconstruction algorithm, an adaptive reconstruction method based on the space-time adaptive processing (STAP) approach [7], [13] and its modifications [12], [14], [15] are proposed, which extract the desired spectrum components from the space-time plane by means of space-time beamforming to obtain the unambiguous full spectrum These methods are adaptive under practical working conditions. The spectrum reconstruction methods and the interpolation reconstruction method are non-adaptive, which are sensitive to channel amplitude-phase error, strong noise and array position error These algorithms first reconstruct the VOLUME 8, 2020 raw data to obtain uniformly sampled data and use frequency domain imaging algorithms, such as Range-Doppler algorithm and Omega-K algorithm, for SAR imaging.
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