2-D radar image is distributed in the range and cross-range domain. High range resolution is obtained by wide bandwidth of the transmitted signal.High cross-range resolution requires a large antenna aperture. Because a large antenna aperture can be synthesized by moving a small real antenna aperture, such imaging radaris called the synthetic aperture radar (SAR). If a radar antenna is stationary, a large aperture can be synthesized by moving or rotating the target. Such imaging radar is called the inverse synthetic aperture radar (ISAR). Figure 1 shows what ISAR images of an airplane and a ship look like.
Figure 1 – Examples of ISAR images of an airplane and a chip.
Any SDR kit can be used as an ISAR for imaging moving targets. For example, C-band SDR-KIT 580AD, X-band SDR-KIT 980AD are oftenbe used for radar imaging of moving targets, such as a moving car. With 2 or more receiver channels, the SDR-KITscan be used as interferometric ISAR or polarimetric ISAR.As an example, Figure 2 shows radar image of a moving vehicle using SDR-KIT 580AD. From radar collected data, translational motion and rotational motion compensationsmust be removed before a range-Doppler image can be formed. Detailed motion compensation algorithms and MATLAB source codes can be obtained from the Reference.
Reference:Victor C. Chen and Marco Martorella, Inverse Synthetic Aperture Radar Imaging – principles, algorithms and applications, IET/Scitech Publishing, 2014.
Figure 2 – Radar image of a moving vehicle generated bySDR-KIT 580AD.