Significance of the additional range-azimuth coupling term in FMCW SAR PTRS

Frequency-Modulated Continuous-Wave (FMCW) Synthetic Aperture Radar (SAR) combines FMCW and SAR techniques which makes a lightweight, high-resolution and cost-effective imaging sensor which can work all weather, day and night. However, the failure of stop-and-go approximation leads to additional range-azimuth coupling terms in the Point Target Reference Spectrum (PTRS) of FMCW SAR. To exploit the influence of these terms in FMCW SAR circumstances, this paper presents the remarkable differences between the spectrum formulations of FMCW SAR and pulsed SAR, and validates the significance of the additional range-azimuth coupling terms introduced by the variation of slant range during the long pulse durations. Simulation experiments proved that ignoring these terms will cause serious reduction of image quality.