为了获得高分辨的合成孔径雷达(SAR)图像,需要采用自聚焦算法对SAR图像进行处理。文中介绍了利用图像对 比度最优准则进行自聚焦的原理方法,将对比度最优自聚焦过程等效为最优一维搜索模型。同时,介绍了变步长搜索黄 金分割算法的原理,首先通过变步长搜索确定搜索区间,然后采用黄金分割法进行迭代收敛,当满足终止条件时,停止迭 代并得到最终的多普勒调频率最优估计值。与现有的算法相比,基于变步长搜索黄金分割优化的自聚焦算法具有收敛速 度快、鲁棒性强的优点。实测数据处理结果验证了算法的有效性。

In order to obtain a high resolution synthetic aperture radar (SAR) image, it is necessary to use the autofocus algorithm for SAR image processing. In this paper, theory of contrast optimization autofocus (COA) algorithm is introduced. The process of COA is described as an optimal one dimension searching model. Then, theory of variable step searching and golden section algorithm is presented. First, convergence region is set by variable step searching. Then, by means of iteration, the golden section method is applied. And the iterative process may be continued until the end condition is met. Finally, the optimal estimation of Doppler chirp rate is acquired. Compared with the existing methods, the proposed algorithm has the advantages of fast convergence speed and strong robust ability. The obtained results prove the validity of this algorithm.

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