Novel autofocus algorithm based on DCT for SAR images
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摘要: 研究了一种基于离散余弦变换(DCT, Discrete Cosine Transform)的SAR(Synthetic Aperture Radar)图像自聚焦算法.该方法从复图像域出发,通过在距离压缩相位历史域引入相位误差模型,改变图像的聚焦程度直至一维像的DCT序列在高序数区域的权值达到最大,从而完成误差校正.同相位梯度自聚焦算法相比,该方法无需在图像域分离出强点目标,因此特别适用于无任何明显特征的图像.由于DCT存在快速算法,使得该自聚焦算法计算量较少,更易实现.实测数据及仿真数据的成像结果证明了此方法的可行性.Abstract: A novel autofocus algorithm for SAR(synthetic aperture radar) images is presented, which is based on DCT(discrete cosine transform). The method, which starts with complex phase-degraded SAR image, after phase errors model is introduced into the range-compressed phase-history domain, carries out phase errors correction by changing the focus until the intensity of the weight function of the azimuth profile in the area of high sequencies is maximized. Compared with the PGA autofocus algorithm, this autofocus algorithm needs not isolate prominent point target in image domain and is especially suitable for the images without specific characteristic. This autofocus algorithm is of less computational complexity and easy to implement, because there are fast algorithms for DCT. The simulation and the processing results of the measured data show the validity of the proposed method.
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Key words:
- SAR(synthetic aperture radar) /
- DCT(discrete cosine transform) /
- autofocus /
- phase errors
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