所涉及的杂波散射体反射率的幅度和相位都必须是恒定的,多散射体188金宝搏

式和的“直流项”表示杂波回波的一个常数非随机分量,有时也称为接收信号的“恒定分量”。

188金宝搏 1

The “DCterm” in Eqs. and represents a constant, nonrandom componentof
the clutter echo that is sometimes called a “persistent component”of the
received signal.

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。

对于这样一种分量的存在,所涉及的杂波散射体反射率的幅度和相位都必须是恒定的。

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

For such a componentto exist, both the amplitude and phase of the
reflectivity of the clutterscatterers involved must be constant.

关于K分布的更多信息请参考附录A。

因此,直流分量可归因于裸露地面、岩石和树干等物体的后向散射。

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

Thus, the DCcomponent is attributable to backscatter from elements such
as bare ground,rocks, and tree trunks.

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。

交流分量解释了运动物体(如树叶、树枝和草的叶片等)的后向散射。

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.

The AC term accountsfor backscatter from moving elements such as leaves,
branches, and blades ofgrass.

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。

简单的自回归滤波器可用于杂波模型的模拟。

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

Simple autoregressivefilters can be used to implement the model in
simulations (Mountcastle, 2004).

具体来说,考虑式的模型,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。

2.3.4.雷达截面的复合模型

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

2.3.4. Compound Models ofRadar Cross Section

这种表示被称为数量波动模型。

如第6章所示,雷达探测性能的预测在很大程度上取决于目标和杂波RCS模型的细节。

This representationis referred to as a number fluctuations model.

As is seen in Chap.6, radar detection performance predictions depend
strongly on the details oftarget and clutter RCS models.

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,式的修改版本可产生K、Weibull、gamma、Nakagami-m或所谓的瑞利混合类分布。

此外,众所周知,雷达散射截面的统计数据随几何结构、分辨率、波长和极化等因素的变化而变化。

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

Furthermore, it iswell known that RCS statistics vary significantly with
a host of factors suchas geometry, resolution, wavelength, and
polarization.

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。

因此,研究良好的统计RCS模型是一个非常活跃的领域。

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.

Consequently, thedevelopment of good statistical RCS models is a very
active area of empiricaland analytical research.

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。

以下是对前面描述的基本建模方法扩展的三个简单示例,所有这些都是由杂波建模的复杂性驱动的。

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

Following are threebrief examples of an extension to the basic modeling
approach described earlier,all motivated by the complexities of modeling
clutter.

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。

由于有关这些模型的文献主要是根据回波幅度ζ而不是RCSσ或功率研究的,本节的其余部分也将集中讨论幅度PDFs。

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

Because theliterature regarding these models is developed primarily in
terms of the echoamplitude ζ instead of RCS σ or power, the remainder of
this sectionalso concentrates on amplitude PDFs.

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。

一些幅度PDF是基于物理动机的,特别是瑞利模型(源自中心极限定理的论证)和Rice或Rician模型(对应于具有额外主要散射源的瑞利模型)。

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

Some amplitude PDFsare physically motivated, especially the Rayleigh
(exponential RCS) model(which follows from a central limit theorem
argument) and the Rice or Ricianmodel (which corresponds to a Rayleigh
model with an additional dominantscattering source).

换句话说,这些小纹波是非均匀分布在海面上的。

其他如对数正态分布或威布尔分布,都是通过对测量数据进行拟合而得到的。

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

Others, such as thelog-normal or Weibull, have been developed
empirically by fitting distributionsto measured data.

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。

188金宝搏 2

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.

该模型已用于描述海杂波。

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。

This model has beenused to describe sea clutter (Jakeman and Pusey,
1976; Ward, 1981).

188金宝搏,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.

随机变量x用一个缓慢去相关的分量来表示,该分量的电压服从自由度为2m的中心chi-square分布,其中m≥2.5。

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

The random variable xis identified with a slowly decorrelating component
having a voltagedistribution following a central chi-square of degree 2m
with m≥2.5.

更多精彩文章请关注微信号:188金宝搏 3

引入该分量是为了解释由于海浪结构和雷达几何引起的“聚束”散射体,并表示幅度平均值随时间的变化。

This component isintroduced to account for “bunching” of scatterers due
to ocean swellstructure and radar geometry, and represents variation in
the mean of theamplitude over time.

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

更多精彩文章请关注微信号:188金宝搏 4

You may also like...

发表评论

电子邮件地址不会被公开。 必填项已用*标注

相关文章

网站地图xml地图