一种新的机载SAR回波高阶多项式相位误差提取方法
doi: 10.3724/SP.J.1146.2006.02018
A New Method to Extract Polynomial Phase Error for Airborne SAR
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摘要: 当载机在SAR回波方位子孔径时间内运动较复杂时,二次相位误差模型不能准确描述载机运动造成的相位误差。针对此情况,该文借鉴PACE算法的思想,提出了一种提取SAR回波中时域高阶多项式相位误差的TPACE算法。TPACE算法将图像对比度函数作为目标函数,以时域高阶多项式相位误差模型系数作为自变量,通过最优化方法提取时域误差系数。文中详细推导了对比度函数关于误差模型系数的梯度表达式,分析了TPACE与以往提取时域高阶多项式相位误差的算法计算量之差别。实际超宽带SAR回波数据处理结果表明,TPACE能有效提取时域高阶多项式误差,是一种计算量相对较小的SAR自聚焦算法。Abstract: When an airborne platform on which Synthetic Aperture Radar (SAR) mounted on flies very complicatedly over subaperture time, traditional quadratic phase error can not depict the errors introduced by the platform motions, and the phase errors need be modeled as polynomial errors with higher order. A new algorithm to extract polynomial errors with higher order from SAR echoes, named as Time Phase Adjustment by Contrast Enhancement (TPACE), is proposed in this paper. The TPACE takes the contrast function as object function and the polynomial coefficients of phase errors as variables to be estimated, directly extracting those coefficients by optimization. The gradient of the contrast function with respect to the variables, which is the key point to implement TPACE algorithm, is derived detailed in the paper. Compared to those existed algorithms that can extract polynomial phase errors, the computation load of TPACE is much less and the TPACE is very useful for real time processing. The results processing real ultra-wide band SAR echoes show the method can extract effectively polynomial phase errors from SAR echoes.
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