例如，很多雷达系统在中频IF完成一些信号处理的工作，而不是完全在基带处理；匹配滤波、脉冲压缩和多普勒滤波都是非常常用的例子。
For example, many systems perform some ofthe signal processing functions at IF rather than baseband; matched filtering,pulse compression, and some forms of Doppler filtering are very common examples.
这里关于信号处理的功能列举也是存在冗余的，某些功能可以根据需要进行裁剪。
The list of signal processing functions isredundant as well.
例如，脉冲压缩和多普勒滤波都可以认为是匹配滤波过程的一部分。
For example, pulse compression and Dopplerfiltering can both be considered part of the matched filtering process.
不同雷达的另一种特性是模拟信号数字化的位置不同。
Another characteristic which differs amongradars is at what point in the system the analog signal is digitized.
较老式的或者现役的大多数雷达都是在基带信号输出之后进行数字化处理。
Older systems are, of course, all analog,and many currently operational systems do not digitize the signal until it isconverted to baseband.
任何在中频IF进行的信号处理都必须用模拟技术完成。
Thus, any signal processing performed at IFmust be done with analog techniques.
新设计的雷达系统越来越多地在中频进行模拟信号数字化，从而将A/D转换器移动到更靠近雷达前端的位置，并使之能够在中频进行数字处理。（中频数字化！！！）
Increasingly, new designs digitize thesignal at an IF stage, thus moving the A/D converter closer to the radar frontend and enabling digital processing at IF.
最后，我们想强调一点，信号处理和数据处理之间的区别有时是不清楚的或者人为的。
Finally, the distinction between signalprocessing and data processing is sometimes unclear or artificial.
在本章接下来的几个部分中，将简要讨论这些雷达子系统的主要特性。
In the next few subsections, the majorcharacteristics of these principal radar subsystems are briefly discussed.
1.3.1发射机与波形产生器
1.3.1. Transmitter and Waveform Generator
发射机和波形产生器是决定雷达灵敏度和距离分辨率的主要因素。（源头是极端重要的！）
The transmitter and waveform generator playa major role in determining the sensitivity and range resolution of radar.
雷达系统的工作频率范围很宽，可以从2MHz到220GHz；激光雷达的工作频率在1012到1015Hz量级，相应的波长约为0.3到30μm。
Radar systems have been operated atfrequencies as low as 2 MHz and as high as 220 GHz (Skolnik, 2001); laserradars operate at frequencies on the order of 1012 to 1015Hz, corresponding to wavelengths on the order of 0.3 to 30 μm (Jelalian, 1992).
然而，大多数雷达工作在大约200MHz至95GHz的微波频段，相应的波长为0.67m至3.16m m。
However, most radars operate in themicrowave frequency region of about 200 MHz to about 95 GHz, with correspondingwavelengths of 0.67 m to 3.16 mm.
表1.1总结了用于普通标准雷达波段的字母命名法（IEEE，1976）。
Table 1.1 summarizes the letternomenclature used for the common nominal radar bands (IEEE, 1976).
Table 1.1. 标准雷达波段的字母命名法Letter Nomenclature for Nominal Radar Frequency Bands
有时候毫米波段被进一步分为36至46GHz(Q频带)、46至56GHz(V频带)和56至100GHz(W频带)的近似子带(Richardset al., 2010)。
The millimeter wave band is sometimesfurther decomposed into approximate subbands of 36 to 46 GHz (Q band), 46 to 56GHz (V band), and 56 to 100 GHz (W band) (Richards et al., 2010).
HF至Ka波段的特定频率由国际协议分配给雷达使用。
Within the HF to Ka bands, specificfrequencies are allocated by international agreement to radar operation.
——本文译自Mark A. Richards所著的《Fundamentals of Radar Signal Processing（Second edition）》
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