Improved RMA based on Nonuniform Fast Fourier Transforms(NUFFT's)

Range Migration Algorithm (RMA) can perfectly fulfill the focusing of the whole scene under the condition of wide aperture and large squint angles. However, Stolt interpolation is needed in regular RMA and is time-consuming. In this paper, an improved RMA algorithm based on Nonuniform FFT (NUFFT) is developed for SAR imaging. NUFFT is substituted for the Stolt interpolation and range IFFT in the improved RMA. In this work, the principle of NUFFT and its implemented steps are analyzed in detail first. Then SAR echo signal model is introduced including the geometric model and the expression of echo signal in both time and frequency domain. Besides, algorithm flow of Regular RMA and the improved RMA based on NUFFT are given. Simulation based on SAR echo model is performed and imaging effects are compared in different squint angles. Numerical simulations illustrate the performance of the improved method. The improved RMA based on NUFFT can satisfy both the imaging precision and computation efficiency.