A simple approach to detecting migration through range-resolution cell for ship ISAR imaging

Inverse synthetic aperture radar (ISAR) imaging consists of two stages. The first stage is motion compensation applied for transforming the relative motion between radar and moving target into the radar´s rotating motion around the target on the turntable. The second stage is range-Doppler (R-D) image formation of the target. Conventional R-D imaging requires that during the coherent integrated time period, the migration of scatters on the target should not be through one range-resolution cell. However, in the case of high-speed angular motion like ship motion with roll, pitch and yaw, the rotating angle may suddenly be increased greatly within the fixed coherent time, which may result in scatter migration through the range resolution cell. This paper presents a method, based on a 1D range profile, to detect whether the change of equivalent profile width exceeds one resolution cell. The approach can select coherent integrated time adaptively so as to satisfy the rotating angle condition. The approach is described and an example is also given to show the efficiency with good focusing in ship ISAR imaging.