Abstract: The change in chirp rate caused by the complex motion of the ship target deteriorates the azimuth focusing quality. This paper proposes a new imaging method based on TC-DechirpClean(DechirpClean searching method based on the time-chirp distribution), which makes use of the changing rate of scatterers’ chirp to search their chirp rate and change rate of the chirp rate in the time-chirp distribution plane. At the same time, we do FFT after compensating the higher-order phase term to acquire the information about the center frequency and magnitude of these scatterers according to the maximum magnitude criteria. Finally, we can reconstruct the echo signal and obtain an instantaneous ISAR image. The imaging result of real data confirms that this method can greatly improve an unfocused ISAR image caused by the change rate of the chirp rate.

Key words: Inverse Synthetic Aperture Radar(ISAR), ship target, chirp, TC-DechirpClean, azimuth focus