An Non-Parametric Rotating Angle Acquisition Method for Optimal ISAR Imaging

Inverse synthetic aperture radar (ISAR) imaging usually consists of two stages. The first is motion compensation applied for transforming the relative motion between radar and moving target into the radar´s rotation motion around the target on the turntable. The second is range-Doppler (R-D) image formation of target. Conventional R-D imaging requires that during the coherent integrated time period, the migration of scatters on target should not be through one resolution cell, otherwise the focusing of edge scatters may be degraded. However, in case of high-speed angular motion like a plane´s big-maneuver flight and ship motion with roll, pitch and yaw, at this time the rotating angle may suddenly be increased greatly within the fixed coherent time which may results in scatter migration through a resolution cell. Therefore, it is necessary to select an appropriate rotating angle for imaging to ensure ISAR imaging results to be focused. Although some research have been reported on this issue, these methods usually need estimation of parameters to realizing ISAR imaging at large rotating angles. In this paper a new idea of acquiring rotating angle for optimal ISAR imaging is presented which is no longer based on the estimation of parameters like rotating angle, rotating speed, etc. The method is described and an example is also given to show the efficiency of new method with good focusing effect in ship ISAR imaging