LAUSR

In view of the error impact of Doppler parameters estimation on SAR imaging performance, this paper constructs the energy focusing axis based on the optimal rotation angle in the optimal range FrFT (fractional Fourier transform) domain. On this basis, the relationship among Doppler center frequency, Doppler FM (frequency modulation) rate, and energy focusing axis, as well as the relationship between Doppler center frequency and Doppler FM rate are derived in detail, and then, the basic framework of the D-FrFT-RD algorithm was constructed. The imaging test of Canadian spaceborne RADARSAT-1 measured data shows that when the error of Doppler center frequency estimation gradually increases from 0% to 5%, the energy focusing axis curve may deviate from the normalized value to some extent, but in reality, the impact on SAR imaging performance parameters is not significant. Compared to the traditional RD (range Doppler) algorithm, the energy focusing axis curve corresponding to the D-FrFT-RD algorithm in this paper is relatively stable, with high range resolution, and varying degrees of improvement in both range PSLR and range ISLR.