Two-Dimensional Spectrum for Circular Trace Scanning SAR Based on an Implicit Function

For circular trace scanning synthetic aperture radar (CTSSAR), the conventional approximated quadratic range equation assumption does not hold due to the impact of the curved flight path. Thus, existing SAR methods cannot focus the target accurately and efficiently in CTSSAR. To address this problem, the stationary phase can be regarded as an implicit function of the Doppler frequency. Therefore, the 2-D spectrum can be consequently achieved by employing the principle of stationary phase. In this letter, an imaging algorithm based on the derived spectrum is developed for CTSSAR. Promising results from simulation demonstrate the validity and effectiveness of the approach.