【读书2】【2014】基于MATLAB的雷达信号处理基础（第二版）——雷达截面的复合模型(1)

因此，以上公式表明，用中心chi分布的几何项调制标准瑞利变量可以解释观测到的海杂波分布。

Thus, the productformulation suggests that modulation of a standard Rayleigh variable by acentral chi-distributed geometric term can account for observed sea clutterdistributions.

关于K分布的更多信息请参考附录A。

Additionalinformation on the K distribution is given in App. A.

最近的研究已经开始弥合散射物理与Ward、Jakeman和Pusey提出的复合杂波模型之间的差距。

More recent researchhas begun to bridge the gap between the physics of scattering and the apparentsuccess of compound clutter models of the type promoted by Ward and Jakeman andPusey.

Sangston总结了“多散射体”物理模型的扩展工作，这些物理模型导致了瑞利分布。

Sangston summarizesthe work on extensions of the “many scatterer” physical model thatleads to the Rayleigh distribution (Sangston, 1994).

具体来说，考虑式（2.50）的模型，但是散射体的数量N是一个随机变量，而不是一个固定常数。

Specifically,consider the model of Eq. (2.50), but let the number of scatterers N be arandom variable instead of a fixed constant.

这种表示被称为数量波动模型。

This representationis referred to as a number fluctuations model.

根据在任何给定时间对回波贡献的散射体数量N的统计数据的选择，式（2.50）的修改版本可产生K、Weibull、gamma、Nakagami-m或所谓的瑞利混合类分布。

Depending on thechoice of the statistics of the number N of scatterers contributing to thereturn at any given time, this modified version of Eq. (2.50) can result in K,Weibull, gamma, Nakagami-m, or any of a number of other distributions in theclass of so-called Rayleigh mixtures.

复合雷达散射截面模型的大部分工作都是在海杂波分析的背景下进行的，而且经验海杂波数据经常被观察到显示出非瑞利统计特性，如威布尔、K和对数正态分布。

Much of the work incompound RCS models has been performed in the context of sea clutter analysis,and empirical sea clutter data have often been observed to exhibit non-Rayleighstatistics such as Weibull, K, and log-normal distributions.

在这种情况下，数量波动模型具有直观的吸引力，因为它与电磁波的物理行为有关。

The numberfluctuation model is intuitively appealing in this case because it can berelated to the physical behavior of waves.

具体地说，散射理论表明，海面上的主要散射体是较小的纹波，而不是大的海浪。

Specifically,scattering theory suggests that the principal scatterers on the ocean surfaceare the small capillary waves, as opposed to the large swells.

这些小的散射中心倾向于聚集在波峰附近，而在波峰之间的区域较少。

These smallscattering centers tend to cluster near the crest of the swells, with fewer ofthem in between.

换句话说，这些小纹波是非均匀分布在海面上的。

In other words, theyare nonuniformly distributed over the sea surface.

因此，当涌浪的波峰进入或离开某个给定的分辨率单元时，照射海面的雷达将接收到来自N个不同数量散射体的回波。

Consequently, a radarilluminating the sea will receive echoes from a variable number N of scatterersas the crests of the swells move into and out of a given resolution cell.

通过对来自不同数量散射体的回波进行求和，采用数量波动模型预测威布尔分布和K分布，并提供了海洋散射现象模型与这些经验观测统计数据之间的联系。

By summing echoesfrom a variable number of scatterers, the number fluctuation model predicts theWeibull and K distributions and provides a link between a phenomenologicalmodel of sea scatter and these empirically observed statistics.

——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing（Second edition）》

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