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Early Warning Radar (EWR): Technology and Signal Processing Algorithms
Radar systems can be classified into two main families according to their application: defense and civilian. Defense radars include air-defense and battlefield radars, whereas civilian radars include weather radars, radars for remote sensing, and others. Air traffic control (ATC) radars can be either defense or civilian. Air defense radars are also subdivided into two more categories: two-dimensional (2-D) and three-dimensional (3-D). The former can measure the target range and azimuth. The latter can determine the target’s height as well. Since air-defense radars can detect targets at great distances (hundreds of kilometers), they can be used as early warning radars (EWRs). A classification of EWRs can be provided based on the platform where the radar is installed. Then, it is possible to distinguish between airborne and ground-based (GB) EWRs. In this chapter, GBEWRs will be discussed. A GBEWR is used primarily for the long-range detection of targets, i.e., allowing defenses to be alerted as early as possible before the intruder reaches its objective, giving the defenses the maximum time in which to operate. The most challenging targets for a GBEWR are ballistic missiles (BMs) because of their small radar cross section (RCS) and the great ranges (hundreds and sometimes even thousands of kilometers) where they are required to be detected. The GBEWRs have a low-measurement resolution, work with low-pulse repetition frequency, and use low-carrier frequencies. The choice of low frequency is supported by the low propagation loss and by the high power that can be transmitted. On the other hand, the resolution and accuracy are limited because a lower frequency requires very large physical antennas. In particular, they work at L- and S-bands (1–2 GHz/2–4 GHz). The best advantage for choosing these bands over very high frequency (VHF) is related to the smaller size of antenna that allows a better compromise between performance and deployability. In addition, the GBEWR can guarantee timely and reliable detection of a high number of targets, which are generally embedded in heavy natural (clutter) and man-made (electronic countermeasures (ECM)) interferences. The target RCS can range from very low (stealth) to relatively high figures. Discriminating false detections from true targets and high accuracy in position finding, even in a multitarget environment (e.g., mass raid), are additional requirements. Finally, target classification, threat assessment, and efficient dissemination of processed data to computer and display systems are facilities that shall be implemented.
De Maio Antonio, Farina Alfonso, Timmoneri Luca, Wicks Michael
Paper for Book
Principles of Modern Radar, vol. 3
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