Inverse Synthetic Aperture Radar Imaging With MATLAB Algorithms

CHAPTER EIGHT

Motion Compensation for Inverse Synthetic Aperture Radar

For the operational inverse synthetic aperture radar (ISAR) situation, the target’s relative movement with respect to the radar sensor provides the angular diversity required for range-Doppler ISAR imagery as given in Chapter 6. For the ground-based ISAR systems, for example, collecting backscattered energy from an aerial target that is moving with a constant velocity for a sufficiently long period of time can provide the necessary angular extend to form a successful ISAR image. On the other hand, real targets such as planes, ships, helicopters, and tanks do have usually complicated motion components while maneuvering. These may include translational and rotational (yaw, roll, and pitch) motion parameters such as velocity, acceleration, and jerk. Moreover, all these parameters are unknown to the radar engineer, which adds further complexities to the problem. Therefore, trying to estimate these motion parameters and also trying to invert the undesired effects of motion on the ISAR image is often called motion compensation (MOCOMP).

Since the motion parameters are unknown to the radar sensor, the MOCOMP process can be regarded as a blind process and is also assumed to be one of the most challenging tasks in ISAR imaging research. The MOCOMP procedure has to be employed in all SAR and ISAR applications to obtain a clear and focused image of the scene or the target. In SAR applications, for example, the information ...