1.7 Receivers for Radar Interception 用于截获雷达信号的接收机

 

The subject of intercept receivers is quite broad because there is no single design or type appropriate for all uses. Generally, intercept receivers can be divided into warning receivers and ELINT receivers.

 

对于截获接收机的设计没有固定的模版，通常根据不同的用途进行考虑，一般可以将其分为告警接收机和ELINT接收机。

 

  Radar warning receivers are designed to give nearly immediate warning if specific threat signals are received (e.g., illumination of an aircraft’s warning receiver by the target tracking radar of a surface-to-air missile system). The warning receiver typically has poor sensitivity and feeds into a near-real-time processor that uses a few parameter measurements to identify a threat. Usually, rough direction (e.g., quadrant or octant) is determined for the threat and the operator has a crude display showing functional radar type, direction, and relative range (strong signals displayed as being nearer than weaker ones). This type of receiver does not provide the kind of output that is analyzed using the methods described here. Rather, the identification algorithms used in the warning receiver might be based on the results of ELINT.

 

告警接收机的作用很简单，主要用于判断是否存在雷达跟踪的威胁。由于告警接收机在雷达探测距离之内发出警报才是有意义的，故不要求太高的灵敏度，但反应速度必须足够快，以摆脱雷达的跟踪。告警接收机通常只能判断雷达类型、威胁的大致方向和相对距离，因此不需要非常复杂的信号处理设备。

 

对于“大致方向”的含义：quadrant, 在二维空间中只需要确定信号处于哪个象限；octant, 则是三维空间中划分的八个区域，分别是：first octant (+++), top-back-right (-++), top-back-left (--+), top-front-left (+-+), bottom-front-left (+--), bottom-back-left (---), bottom-back-right (-+-), bottom-front-right (++-)。

 

  ELINT receivers must cope with a wide variety of signal parameters. The signals of interest extend over a wide dynamic range – wider than any receiver design can hope to handle due to the tremendous range differences possible and the different radar effective radiated power (ERP) values that may be encountered. The ELINT receiving equipment must cover a wide frequency range to be able to search for new radars in any part of the spectrum. Coverage to 100 GHz may be needed. The modulation bandwidths of the signals can range from very short pulses to those of frequency modulation (FM) and continuous wave (CW) signals. The receiving equipment may also be operated remotely with automatic digitizing and/or retransmission to analysis sites. ELINT receivers may be found in a variety of locations, including ships, aircraft, balloons, and ground locations. Often this places them in proximity to local radar sets or jammers. In this case, it is generally necessary to provide for blanking of the ELINT receiver during the transmission cycle of these local emitters. Receivers are discussed in Chapter 3.

 

ELINT接收机的目的是截获尽量多的雷达信号并进行详细分析，以确定对方的战术与战略企图，同时将截获的雷达样本建立数据库供信号分选识别之用。ELINT接收机所处的位置很灵活，可以接近目标也可以远离目标，故需要满足大动态范围、宽频段（可高达100GHz）、系统带宽可调等性能指标，因此ELINT接收机通常十分复杂。

  为了对告警接收机和ELINT接收机进行直观的对比，下面给出几个例子：

从两种接收机的性能指标数目的比较就可以看出，ELINT接收机的设计远比告警接收机复杂，也许可以这样说，告警接收机是战术型的，而ELINT接收机是战略型的。

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