高分辨率合成孔径雷达的相干斑是由雷达信号的干性引起的，并存在于所有相干图像中。根据SAR成橡机理，分析了产生的原因特征，给出了SAR相干斑的确切定义、统计方法。实验表明统计结果与传统方法相比更加精确。

Speckle noise in high-resolution synthetic aperture radar (SAR) images is generated by the coherent processing of radar signals and exists in all types of coherent images systems. In this paper we study the characteristics and statistical properties of speckle noise in SAR image, redefine the speckle definition, analyse the reasons about the speckle noise generation and, give the statistics formula. The experimental results indicate the statistics result is more precise than the traditional statistics result. The theory of interferometry has been used to increase resolution of the radar, but the aberrance target will appear on the SAR image thus result in the reduction of SNR reduce, while electromagnetic waves irradiate target. The interaction of the transmitted wave and echo wave as well as the transmitted wave of other objects results in speckle, which is one of the most important characters of the SAR image. SAR image doesn't directly display the spectrum characteristic of the point target, but displays the scattering characteristic. During the movement of the radar, the interaction of the transmitted wave, echo wave and other noise wave results in distortion of the echo wave. The speckle is considered traditionally as pixels, whose breadth is more than the mean breadth variance. However the traditional definition doesn't completely reflect the characteristic of the aberrance target in SAR image. This paper based on the characteristic of the echo wave analyses the cause of the speckle during the period of the emission, take-over, data transmission, echo demodulation and imaging process of the radar signal. According to the characteristic of the echo wave area in SAR image, this paper brings forward the definition of the speckle, and the method of analysis and statistic for the characteristic. This paper creates the mathematics model and the methods for computing the speckle by means of averaging energy of each echo wave of the target. Thus the natural characteristic of the speckle in SAR image can be accurately reflected. Our result will contribute to the research of the interferometric SAR.