A Fast ISAR (Inverse Synthetic Aperture Radar)-Imaging Process and Its Inherent Degrading Effects on Image Quality,

A method for a fast two-dimensional inverse synthetic aperture radar ISAR imaging process is presented. A coherent short pulse radar is used to sample amplitude and phase of the backscattered field from a continuously rotating object. This is being done while a narrow range gate is sweeping in range steps of 15 cm across the target plane at a typical speed of 150 ms. Applying fast synthetic aperture radar SAR principles, in an off-line process for each range cell an acceptable good cross-range resolution can be obtained when processing angle intervals of less than 30. The influence of analytical approximations as well as the effect of moving scattering centers through several range resolution cells during the process interval can cause severe image degradations. Two methods for partial and complete compensation of these effects under the aspect of minimum loss in processing speed have been developed and will be presented here.