ISAR image simulation of targets with moving parts using the shooting and bouncing ray technique

The inverse synthetic aperture radar (ISAR) image of a target is very useful in radar signature applications. For instance, they can be used as a diagnostic tool to pinpoint the key scattering centers on the target, or as an identification tool to distinguish and classify the target from a collection of possible targets. ISAR image of a target is typically formed either by Fourier processing the monostatic/bistatic scattered field data over a finite range of look angles and frequencies or by using the range-Doppler methodology. In the range-Doppler imaging scheme the ISAR images are generated under the assumption that the target is rotating with a known angular velocity. The Doppler frequency shifts from different parts of the target are then linearly related to the cross-range location of the scatterers on the target. Under dynamic situation when there are moving parts on the target, e.g., rotating engine blades on an aircraft, additional Doppler shifts are produced which strongly affect the ISAR image. The simulation of the moving parts effect is therefore an important problem for understanding and identification of this phenomenon. We describe a simple methodology for simulating the ISAR image of a target with arbitrary moving parts using the shooting and bouncing ray (SBR) method.