一种非常常见的选择波形是线性调频（LFM或“啁啾”），如图1.21a所示。

A very common choice is the linearfrequency modulated (linear FM, LFM, or "chirp") waveform, shown inFig. 1.21a.

Figure 1.21. (a)线性调频波形调制函数，瞬时频率随时间增大。(b)图(a)的LFM波形的匹配滤波器输出 (a)Linear FM waveform modulation function, showing an increasing instantaneousfrequency. (b) Output of the matched filter for the LFM waveform of (a).

在脉冲持续期间，LFM脉冲的瞬时频率扫过期望的带宽；频率可以上扫或下扫，但是频率变化的速率是恒定的。

The instantaneous frequency of an LFM pulseis swept over the desired bandwidth during the pulse duration; the frequencymay be swept either up or down, but the rate of frequency change is constant.

根据定义，匹配滤波器是雷达接收机中用于最大化其输出信噪比的滤波器。

The matched filter is by definition afilter in the radar receiver designed to maximize the SNR at its output.

具有这种特性的滤波器脉冲响应已经被证明是发射波形调制函数的复制品，该调制函数在时间上被反转并且取共轭，因此滤波器的脉冲响应与特定的发射波形调制“匹配”。

The impulse response of the filter havingthis property turns out to be a replica of the transmitted waveform'smodulation function that has been reversed in time and conjugated; thus theimpulse response is "matched" to the particular transmitted waveformmodulation.

脉冲压缩是设计波形及其相应的匹配滤波器的过程，使得响应于来自单点散射体的回波经过匹配滤波器后，在很短的持续时间内集中其大部分能量，从而提供良好的距离分辨率，同时仍然允许使用长脉冲的高发射能量。

Pulse compression is the process ofdesigning a waveform and its corresponding matched filter so that the matchedfilter output in response to the echo from a single point scattererconcentrates most of its energy in a very short duration, thus providing goodrange resolution while still allowing the high transmitted energy of a longpulse.

图1.21b显示了对应于图1.21a的LFM脉冲的匹配滤波器输出；注意，输出响应的主瓣比原始脉冲的持续时间窄得多。

Figure 1.21b shows the output of thematched filter corresponding to the LFM pulse of Fig. 1.21a; note that the mainlobe of the response is muchnarrower than the duration of the original pulse.

第四章介绍了匹配滤波、脉冲压缩和波形设计的概念，以及线性调频和其它常见波形的特性。

The concepts of matched filtering, pulsecompression, and waveform design, as well as the properties of linear FM andother common waveforms, are described in Chap. 4.

时域主瓣的3-dB宽度近似为1/β秒，其中β为波形的瞬时带宽。

There it is seen that the 3-dB width of themainlobe in time is approximately 1/β seconds, where β is the instantaneousbandwidth of the waveform used.

波形的时域宽度决定了距离上分辨目标的能力。

This width determines the ability of thewaveform to resolve targets in range.

转换为等效距离单位，距离分辨率为

Converted toequivalent range units, the range resolution is given by

这与前面给出的等式(1.2)相同。

This is the same as Eq. (1.2) presentedearlier.

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

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