Long-distance imaging with frequency modulation continuous wave and inverse synthetic aperture radar

In a frequency modulation continuous wave and inverse synthetic aperture radar (FMCW-ISAR) system, imaging a target beyond the maximum unambiguous range causes the ambiguity in the range domain. This ambiguity phenomenon greatly reduces resolution and degrades image quality, and limits the application of long-distance imaging of an FMCW-ISAR system. In this study, ambiguity correction method, based on mutual-coherence processing, is proposed for long-distance imaging in an FMCW-ISAR system. In the process, the singularity point of the beat signal caused by the ambiguity phenomenon is determined by the wavelet transform modulus maxima method. All-pole models are used to fit the beat signal subbands of different Doppler frequencies, and then adjust the models until they optimally match. The simulation results validate the effectiveness of the proposed correction method. This study shows the promising prospect of long-distance imaging using an FMCW-ISAR system.