4Inverse Synthetic Aperture Radar Imaging and Its Basic Concepts

Inverse synthetic aperture radar (ISAR) is a powerful signal processing technique for imaging moving targets in range‐Doppler (or range and cross‐range) domains. ISAR processing is normally used for identifying and classifying targets. As range (or slant range) is defined as the axis parallel to the direction of propagation from radar toward the target, cross‐range is defined as the perpendicular axis to the range direction. An ISAR image has the ability of successfully displaying the dominant scattering regions (hot points), i.e., scattering centers on the target. The classical 2D ISAR image is constructed by collecting the scattered field for different look angles and Doppler histories. Although ISAR processing is similar to SAR processing, ISAR imaging procedure has some conceptual differences when compared to the SAR imagery.

4.1 SAR versus ISAR

SAR generally refers to the case when radar platform is moving while the target stays stationary (see Chapter 3, Figures 3.1 and 3.4). The required spatial (or angular) diversity is accomplished by the radar movement around the target or terrain. On the other hand, the term ISAR is used for scenarios when the radar is stationary and the targets are in motion such as airplanes, ships, and tanks as illustrated in Figure 4.1. As similar to the SAR operation, the required range resolution is achieved by using finite frequency bandwidth of the transmitted signal for the ...

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