Imaging of space targets in FMCW-ISAR

Combining Frequency Modulation Continuous Wave (FMCW) and Inverse Synthetic Aperture Radar (ISAR), FMCW-ISAR is more practical with low cost, low power, small volume for short distance targets. However, the continuous echo signals in FMCW-ISAR system lead to dechirp distortion phenomenon during the process of dechirp for far-distance targets, especially for the space targets. In this paper, a signal model is proposed to study the image processing of space targets in FMCW-ISAR system. The effects of dechirp distortion which can be ignored for short-distance targets are analyzing for the first time. Double images of a target appear after imaging because of the distortion which decreases the resolution. A method is proposed to correct the distortion by translating the current received signal according to the acquired reference distance. The simulation results validate the theoretical analysis conclusions and the effectiveness of the proposed method for the distortion correction.