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Open AccessArticle

Focusing of Ultrahigh Resolution Spaceborne Spotlight SAR on Curved Orbit

Key Laboratory of Radar Imaging and Microwave Photonics, Ministry of Education, College of Electronic Information Engineering, Nanjing University of Aeronautics and Astronautics, 29 Jiangjun Avenue, Nanjing 210016, China
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Electronics 2019, 8(6), 628; https://doi.org/10.3390/electronics8060628
Received: 11 April 2019 / Revised: 27 May 2019 / Accepted: 30 May 2019 / Published: 3 June 2019
Aiming to acquire ultrahigh resolution images, algorithms for spaceborne spotlight synthetic aperture radar (SAR) imaging typically confront challenges of curved orbit and azimuth spectral aliasing. In order to conquer these difficulties, a method is proposed in this paper to obtain ultrahigh resolution spaceborne SAR images on a curved orbit, which is composed of the modified RMA (Range Migration Algorithm) and the modified deramping-based approach. The modified RMA is developed to deal with the effect introduced by a curved orbit and the modified deramping-based approach is utilized to handle the problem of azimuth spectral aliasing. In the modified RMA, the polynomial expression of SAR two-dimensional spectrum on a curved orbit is derived with fourth-order azimuth phase history model and series reversion. Then, the singular value decomposition (SVD) is applied to decompose the expression of SAR two-dimensional spectrum numerically in order to acquire coordinates for Stolt interpolation in the scenario of curved orbit. In addition, the modified deramping-based approach is derived by introducing orbital state vectors in order to accommodate the situation of curved orbit in the proposed method. Experiments are implemented on point target simulation in order to verify the effectiveness of the presented method. In experiments, the range and azimuth resolution can achieve 0.15 m and 0.14 m, with focused scene size of 3 km by 3 km. View Full-Text
Keywords: ultrahigh resolution; synthetic aperture radar (SAR); spaceborne; curved orbit; series reversion; singular value decomposition (SVD); deramping-based approach ultrahigh resolution; synthetic aperture radar (SAR); spaceborne; curved orbit; series reversion; singular value decomposition (SVD); deramping-based approach
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Qian, Y.; Zhu, D. Focusing of Ultrahigh Resolution Spaceborne Spotlight SAR on Curved Orbit. Electronics 2019, 8, 628.

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