The current windowing method and prominent point selection of phase gradient autofocus （PGA） algorithm are not generalized, therefore this paper presents an improved algorithm for the PGA, The algorithm presents a new method to determine the point spread function support domain of the phase error, which calculates the average energy distribution of azimuth direction as the average energy outside the support domain, in order to determine the width of the window. Based on this adaptive windowing method, this paper also proposes an improved method of selecting prominent point, which can select the prominent points of big signal-to-noise ratio （SNR） and remove the prominent points of small SNR, Compared to the traditional windowing method and prominent point selection, the method of this paper can get a better focus result, which is demonstrated by the exneriment.%针对现有的相位梯度自聚焦（phase gradient autofocus，PGA）算法的加窗方法和特显点选取所存在的问题，提出一种改进的PGA算法。该算法提出一种新的确定相位误差点扩展函数支撑域的方法，此方法计算方位向上能量分布的平均值作为支撑域外的平均能量，以此来确定加窗的宽度。基于这种自适应加窗方法，还提出一种改进的特显点选取方法，该方法能够选择信杂比大的特显点，去掉信杂比小的特显点。试验结果表明，与传统的加窗方法和特显点选取方法相比，该方法能够得到更好的聚焦效果。
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