Estimation of three-dimensional motion parameters in interferometric ISAR imaging

In most interferometric inverse synthetic aperture radar (InISAR) systems, the pixels between two ISAR images derived from corresponding antennas usually do not register properly. As such, correct phase difference between two ISAR images could not be obtained. A three-dimensional (3-D) motion compensation method, or 3-D focusing, is put forward in this paper. With a multiple antenna pair configuration, the angular motion parameters both in the azimuth and pitching directions are accurately estimated without the usual phase-unwrapping processing. As such, there is no phase ambiguity in the inteferometric systems. The angle motion trajectory measurement here is based on the range profiles (or spatial spectrum) so that the "angle scintillation" phenomenon can be effectively suppressed. The angular motion trajectory is then obtained by curve fitting of the spatial spectrum (range profile in the cross-range direction). The compensated ISAR images are registered accurately. Finally, the simulation data are used to illustrate the accuracy of the proposed method.