杂波滤波和多普勒处理密切相关。

Clutter filtering and Doppler processingare closely related.

这两种技术都是通过抑制来自杂波回波的干扰来提高运动目标的可检测性，杂波通常来自天线视场中的地形反射；由于杂波和感兴趣目标回波的多普勒频移存在差异，因此能够在多普勒频域进行有效区分。

Both are techniques for improving thedetectability of moving targets by suppressing interference from clutterechoes, usually from the terrain in the antenna field of view, based ondifferences in the Doppler shift of the echoes from the clutter and from thetargets of interest.

在使用这些术语的历史上，主要区别在于它们是在时域还是在频域进行实现的。

The techniques differ primarily in whetherthey are implemented in the time or frequency domain and in historical usage ofthe terminology.

杂波滤波通常采用运动目标指示(MTI)的形式，即简单地对给定范围内的雷达回波进行脉冲之间的高通滤波，以抑制假定为非运动杂波引起的恒定分量。

Clutter filtering usually takes the form ofmoving target indication, or MTI, which is simply pulse-to-pulse highpassfiltering of the radar echoes at a given range to suppress constant components,which are assumed to be due to nonmoving clutter.

极其简单、非常低阶(通常为一阶或二阶)的数字滤波器在时域中应用于固定范围的连续发射脉冲上采集的回波样本。

Extremely simple, very low-order (mostcommonly first- or second-order) digital filters are applied in the time domainto samples taken at a fixed range but on successive transmitted pulses.

术语“多普勒处理”通常意味着使用快速傅立叶变换算法，或者有时使用某些其它频谱估计技术，来显式地计算在多个脉冲固定范围上回波数据的频谱。

The term "Doppler processing"generally implies the use of the fast Fourier transform algorithm, oroccasionally some other spectral estimation technique, to explicitly computethe spectrum of the echo data for a fixed range across multiple pulses.

由于其不同的多普勒频移，来自运动目标的能量集中到非杂波多普勒频谱的其它不同位置，从而允许检测并分离目标。

Due to their different Doppler shifts,energy from moving targets is concentrated in different parts of the spectrumfrom the clutter energy, allowing detection and separation of the targets.

多普勒处理能够从雷达信号中获得比MTI滤波更多的信息，如运动目标的数目和近似速度。

Doppler processing obtains more informationfrom the radar signals, such as number and approximate velocity of movingtargets, than does MTI filtering.

但多普勒处理需要更多的雷达相干脉冲，从而消耗更多的能量、时间和运算量。

The cost is more required radar pulses,thus consuming energy and timeline, and greater processing complexity.

许多系统将这两种技术进行串联使用。

Many systems use both techniques in series.

杂波滤波和多普勒处理是第五章的主题。

Clutter filtering and Doppler processingare the subjects of Chap. 5.

1.5.4. 成像

1.5.4. Imaging

大多数人都很熟悉雷达在屏幕上产生“闪烁”来表示目标的场景，事实上，设计用来检测和跟踪运动目标的系统都可以做到这一点。

Most people are familiar with the idea of aradar producing "blips" on a screen to represent targets, and in factsystems designed to detect and track moving targets may do exactly that.

然而，也可以设计雷达来计算场景中的高精度分辨率图像。

However, radars can also be designed tocompute fine-resolution images of a scene.

图1.22将90年代中期常规获得的SAR图像与同一场景的航空照片质量进行比较，仔细对比可以发现在雷达和可见波长上的场景外观具有许多相似点和许多显著差异。

Figure 1.22 compares the quality routinelyobtainable in SAR imagery in the mid-1990s to that of an aerial photograph ofthe same scene; close examination reveals many similarities and manysignificant differences in the appearance of the scene at radar and visiblewavelengths.

Figure 1.22. 阿尔布开克机场光学图像与SAR图像比较。（a）K波段（15GHz）SAR图像，3米分辨率。（b）航空照片。Comparison of optical and SAR images of the Albuquerque airport. (a)K band (15 GHz) SAR image, 3-m resolution. (b) Aerial photograph. (Imagescourtesy of Sandia National Laboratories. Used with permission.)

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

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