An Efficient Imaging Approach for Tops Sar Data Focusing Based on Scaled Fourier Transform

This paper presents an efficient imaging algorithm for Terrain Observation by Progressive Scans (TOPS) mode SAR raw data focusing. First, the use of subaperture is adopted to overcome the aliased Doppler spectra due to progress azimuth beam scanning. Afterwards, range compression and range cell migration correction (RCMC) are individually implemented in each azimuth block with its individual Doppler centroid. After azimuth subaperture signal recombination, a new Doppler centroid varying rate is introduced to avoid the reconstructed Doppler spectra wrapping. Moreover, azimuth varying beam center time is removed by azimuth frequency scaling before the final azimuth spectrum analysis (SPECAN) step. Finally, the conventional Fourier transform (FT) is replaced by the scaled Fourier transform (SCFT) step to obtain the uniform azimuth space sampling interval. Since the proposed imaging algorithm is without any interpolations and azimuth data extension, it is highly efficient. Simulation results on point targets validate the proposed algorithm.