Autofocus correction of residual low-order and high-frequency phase error in synthetic aperture radar

Qianrong Lu; Yesheng Gao; Kaizhi Wang; Xingzhao Liu

doi:10.1117/1.JRS.11.035015

12 September 2017 Autofocus correction of residual low-order and high-frequency phase error in synthetic aperture radar

Qianrong Lu, Yesheng Gao, Kaizhi Wang, Xingzhao Liu

Author Affiliations +

Journal of Applied Remote Sensing, Vol. 11, Issue 3, 035015 (September 2017). https://doi.org/10.1117/1.JRS.11.035015

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.

Citation Download Citation

Qianrong Lu, Yesheng Gao, Kaizhi Wang, and 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

Received: 11 April 2017; Accepted: 16 August 2017; Published: 12 September 2017

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