例如，在所有其它条件都相同的情况下，如果发射更大的功率，则接收到的回波信号更强。

For example, if more power is transmitted amore powerful received echo is expected, all other things being equal.

在第二章建立了与信号处理器设计相关的典型测量信号的行为模型。

In Chap. 2, models of the behavior oftypical measured signals that are relevant to the design of signal processorsare developed.

雷达距离方程将给出一种预测信号功率的方法。

The radar range equation will give a meansof predicting signal power.

通过多普勒现象可以预测接收信号的频率。

The Doppler phenomenon will predictreceived frequency.

可以看出，真实世界的复杂性引起了雷达信号的非常复杂的变化；这将导致使用随机过程来模拟信号，以及采用特定的概率密度函数来很好地匹配雷达系统的测量行为。

It will be seen that the complexity of thereal world gives rise to very complex variations in radar signals; this willlead to the use of random processes to model the signals, and to particularprobability density functions that match measured behavior well.

我们将简要概述地面和海面回波随测量几何和雷达特性变化的行为。

A (very) brief overview of the behavior ofthe variation of ground and sea echo with sensing geometry and radarcharacteristics will be given.

我们还将看到，所测量的信号可以表示为理想测量的“真实”信号与雷达波形(在距离维)或天线方向图(在方位或俯仰维，两者也称为横向距离维)的卷积。

It will also be shown that measured signalscan be represented as the convolution of the "true" signalrepresenting the ideal measurement with the radar waveform (in the rangedimension) or its antenna pattern (in the azimuth or elevation dimension, bothalso called cross-range dimension).

因此，随机过程和线性系统理论的结合将用于描述雷达信号，并用于设计、分析雷达信号处理器。

Thus, a combination of random process andlinear systems theory will be used to describe radar signals and to design andanalyze radar signal processors.

1.5.3. 信号调理与干扰抑制

1.5.3. Signal Conditioningand Interference Suppression

图1.18中的天线之后的前几个模块可以被认为是信号调理操作，其目的是在检测、参数测量或成像操作之前提高数据的SIR。

The first several blocks after the antennain Fig. 1.18 can be considered as signal conditioning operations whose purposeis to improve the SIR of the data prior to detection, parameter measurement, orimaging operations.

也就是说，这些模块的目的是尽可能地“清理”雷达数据中包含的干扰因素。

That is, the intent of these blocks is to"clean up" the radar data as much as possible.

该功能通常通过固定和自适应波束形成、脉冲压缩、杂波滤波和多普勒处理的组合来实现。

This is done in general with a combinationof fixed and adaptive beamforming, pulse compression, clutter filtering, andDoppler processing.

当雷达天线为阵列构型时，即，当信号处理器有多个相位中心信号或信道可用时，波束形成方案是适用的。

Beamforming is applicable when the radarantenna is an array, i.e., when there are multiple phase center signals, orchannels, available to the signal processor.

固定波束形成是组合各种可用相位中心的输出，以形成类似于图1.6所示的定向增益方向图的过程。

Fixed beamforming is the process ofcombining the outputs of the various available phase centers to form adirective gain pattern, similar to that shown in Fig. 1.6.

通过高增益主瓣和低旁瓣设计，可以有选择地增强来自天线视线方向上散射体的回波强度，同时抑制来自其它方向上的散射体(通常是杂波)回波。

The high-gain mainlobe and low sidelobesselectively enhance the echo strength from scatterers in the antenna lookdirection while suppressing the echoes from scatterers in other directions,typically clutter.

只要干扰机的辐射方向不在天线的主瓣内，旁瓣还能提供干扰信号的抑制措施。

The sidelobes also provide a measure ofsuppression of jamming signals so long as the angle of arrival of the jammer isnot within the mainlobe of the antenna.

通过适当选择用于组合各通道的权值，可以把天线波束的主瓣转向不同的观测方向，并且可以改变旁瓣电平和主瓣宽度(角度分辨率)之间的折衷关系。

By proper choice of the weights used tocombine the channels, the mainlobe of the beam can be steered to various lookdirections, and the tradeoff between the sidelobe level and the mainlobe width(angular resolution) can be varied.

自适应波束形成使这一思想更进一步。

Adaptive beamforming takes this idea a stepfurther.

通过不同通道接收数据的相关性质，可以识别出进入天线方向图旁瓣的干扰和杂波，并且可以设计用于组合通道数据的一组权值，使得天线不仅具有高增益主瓣和比较低的旁瓣，而且在干扰机到达角的方向上形成零陷。

By examining the correlation properties ofthe received data across channels, it is possible to recognize the presence ofjamming and clutter entering the antenna pattern sidelobes and design a set ofweights for combining the channels such that the antenna not only has ahigh-gain mainlobe and generally low sidelobes, but also has a null in theantenna pattern at the angle of arrival of the jammer.

用这种方法可以获得更大的干扰抑制效果。

Much greater jammer suppression can beobtained in this way.

类似地，也可以通过该技术增强杂波抑制能力。

Similarly, it is also possible to increaseclutter suppression by this technique.

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

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