Experimental Investigations on the Distortion of ISAR Images Using Different Radar Waveforms

摘要

The Inverse Synthetic Aperture Radar (ISAR) image of a target can be distorted as a result of a small perturbing motion possessed by the target. This has been observed regularly in radar imaging of moving targets such as in-flight aircraft, ships sailing on high seas and maneuvering ground vehicles. A Target Motion Simulator apparatus that simulates a target with small perturbing motion has been designed and built to study the ISAR distortion experimentally. A series of measurements under controlled conditions have been conducted to collect the distorted ISAR image data. The experimental results show that severe distortion in the ISAR image can occur as a result of small perturbing motion from the target. Two different radar waveform types, pulse compression and stepped frequency, are used in the investigation. The purpose is to determine whether the radar waveform plays a role in the distortion of ISAR images. A systematic analysis has been carried out to characterize the ISAR distortion. Results indicate that the distortion is independent of the radar waveform used. This information will be useful for developing image refocusing procedures to restore distorted ISAR images for target identification applications.