1.9 The Impact of LPI Radar on ELINT 低截获概率雷达对ELINT的影响

 

Since ELINT has such value, a natural direction for radar design would be to reduce the ability of a would-be listener to receive the radar signal. Such radar systems are said to have low probability of intercept features. These may include low sidelobe antennas, infrequent scanning, reducing the radar power when tracking a closing target (as range is reduced, the radar power is also reduced), making use of waveform coding to provide transmitting duty cycles approaching one (to reduce peak power while maintaining the required average power), and using frequency hopping to force the interceptor to consider more of the spectrum in attempting to characterize the radar.

 

低截获概率（LPI）雷达技术包括低旁瓣天线、减少扫描次数、自适应调整发射功率（根据目标距离的远近）、波形编码（在降低峰值功率的同时保持需要的平均功率）、频率跳变等。

 

  The problem of LPI radar design is fundamentally quite different. Search via radar is analogous to using a searchlight to spot an airplane at night. Energy is sent out, reflected by the target and used by the observer to spot the airplane. An LPI-type searchlight design still would require that the airplane be spotted, but also that the searchlight itself could not be seen by an observer. Because of the fundamental nature of this problem, it requires careful analysis. LPI radar is considered in some detail in Chapter 9.

 

LPI雷达对ELINT接收机的设计提出了更严峻的挑战。

 

  The problems inherent in LPI radar design are such that electronically intercepted signal information will continue to be available; however, new approaches for interception of LPI-type radars will be needed.

 

矛与盾的较量永不停止。

 

  The design and use of intercept receivers is heavily influenced by the design of radar systems: today’s intercept receivers reflect the radar signals in use today; tomorrow’s intercept receivers will reflect tomorrow’s radar signals. From the earliest days of radar until recent times, radar designers have not been directly concerned with the activities of would-be interceptors. Their aim has been to produce well-designed radars capable of performing specified functions without regard to the activities of ELINT operations. Of course, radar designers and operators have always been concerned with chaff and jamming or electronic attack, and have taken steps to reduce their effects through electronic counter-countermeasures (ECCM) or electronic protection (EP) [6].

 

雷达技术的发展必将促进ELINT接收机的发展。

 

  If the LPI philosophy of radar design influences the signal emissions of tomorrow’s radar systems, the designers of intercept receivers must respond (as best they can) to be successful, where possible, in spite of the LPI design approaches which may be adopted. (The LPI radar designer makes a strategic mistake by assuming that intercept receiver designs will not change in response to introducing LPI radar into the signal environment.)

 

低截获的概念实际上不是很科学，只有针对特定的雷达和ELINT接收机，讨论截获概率才是有意义的。在不了解对手之前，任何结论都毫无用处。

 

  Another influence on radar design is efforts to reduce the radar cross section of targets. This makes LPI design more difficult because the lower the target’s radar cross section, the more average power required by the radar to detect the target. Radar systems are evolving in the direction of multiple functions and multiple modes. Future radars may well have both LPI and low target cross section modes among many others in their repertoire.

 

为了躲避雷达的追踪，目标的反射截面越来越小，使得LPI的实现困难增大。因此，雷达不仅要完成目标的检测，还要躲避ELINT的威胁。

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