式（2.49）中的每一个累加项表示来自单个散射体的回波。

Each term in Eq.(2.49) represents the echo from a single scatterer.

该方程突出了这些回波信号的一个极其重要的特征。

This equationhighlights an extremely important characteristic of these echoes.

除了通过散射体的反射率进行幅度缩放外，式中的每一项还相对于载波信号进行相位偏移，相位偏移量为–4πR/λ弧度。

In addition to beingscaled by the scatterer reflectivity, each term is also phase-shifted relativeto the carrier by the amount –4πR/λ radians.

正如我们将会看到的，这种与距离相关的相移为最基本的相干雷达信号处理操作（如多普勒处理、成像和自适应波束形成）提供了基础。

As will be seen, thisrange dependent phase shift provides the basis for most fundamental coherentradar signal processing operations such as Doppler processing, imaging, andadaptive beamforming.

相移是一个非常敏感但又容易模糊的距离变化指示量，因为距离上的每一个λ/2变化都会产生一个2π的相位变化。

The phase shift is avery sensitive, but also very ambiguous, indicator of range changes since everyλ/2 change in range produces a 2π change in phase.

对于复杂目标，如图2.6所示的RCS变化将非常复杂，因为复杂目标是具有许多不同独立RCS的散射体。

RCS variations likethose of Fig. 2.6 become very complicated for complex targets having manyscatterers of varying individual RCS.

图2.8显示了一个由50个点散射体组成的“目标”，这些散射体随机分布在一个5 m宽、10 m长的矩形内。

Figure 2.8 shows a"target" consisting of 50 point scatterers randomly distributedwithin a rectangle 5 m wide and 10 m long.

Figure 2.8. 用于获得图2.9的50个散射体的随机分布示意图Random distribution of50 scatterers used to obtain Fig. 2.9

每个独立的点散射体RCS均为常数，即σ_i= 1.0。

The RCS of eachindividual point scatterer is a constant, σ_i = 1.0.

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

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