12 September 2017 Autofocus correction of residual low-order and high-frequency phase error in synthetic aperture radar
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Abstract
Due to the presence of atmospheric turbulence, motion error (ME) arises and causes residual azimuth phase error (APE) during synthetic aperture radar (SAR) data acquisition. APE can degrade SAR images, especially for light-weight SAR. Moreover, different kinds of APE have different impacts on the image, which makes it hard to compensate for. A parametric autofocus based on a cost metric consisting of the modified entropy and the residual entropy (MERE) is developed to compensate the APE. This approach using the optimization transfer method aims to minimize the MERE. The polynomial decomposition is applied to fit the low-order APE while inverse discrete cosine transform model is adopted for the high-frequency case. Additionally, we also design a modified adaptive-order search strategy, and it helps to remarkably reduce the computational load while maintaining accuracy. In the case of correcting high-frequency APE, the MERE metric could effectively avoid the over-fitted problem that arises in entropy-based autofocus. The real airborne SAR data experiments and comparisons demonstrate the validity and effectiveness of the proposed autofocus.
© 2017 Society of Photo-Optical Instrumentation Engineers (SPIE)
Qianrong Lu, Qianrong Lu, Yesheng Gao, Yesheng Gao, Kaizhi Wang, Kaizhi Wang, Xingzhao Liu, Xingzhao Liu, } "Autofocus correction of residual low-order and high-frequency phase error in synthetic aperture radar," Journal of Applied Remote Sensing 11(3), 035015 (12 September 2017). https://doi.org/10.1117/1.JRS.11.035015 . Submission: Received: 11 April 2017; Accepted: 16 August 2017
Received: 11 April 2017; Accepted: 16 August 2017; Published: 12 September 2017
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