KEYWORDS: Synthetic aperture radar, Radar, Reflectors, Data modeling, Systems modeling, Image processing, L band, Imaging systems, Time metrology, Fourier transforms
Ionospheric dispersion would change with time and space for Geosynchronous Synthetic Aperture Radar (GEO SAR) systems, which causes a significant de-correlation of radar echoes during the long-time synthetic aperture process and seriously influences the imagery quality in azimuth. To address the issue, a parametric autofocus method by the ionospheric dispersion compensation for GEO SAR systems is proposed in the article. Firstly, the GEO SAR signal model is given, where the phase variations due to the ionospheric dispersion is characterized with the polynomial model. Then, the SAR imaging expression with the Back-Projection (BP) imaging method is utilized to estimate the polynomial parameters for the current GEO SAR echoes based on the Minimum Entropy Criterion of the SAR imagery. Thus, the temporal and spatial phase variations can be properly compensated with the polynomial and the imagery is well focused. Finally, the experimental results based on the ground slide rail indicate the usefulness of the proposed method.
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