The Study Of Signal Processing For Synthetic Aperture Radar Based On The Fractional Fourier Transform

As modern SAR systems are continuously developing into the direction of higherspatial resolution, the research of imaging algorithm techniques for SAR systems hasan important realistic significance. On the basis of studying the fractional Fouriertransform and SAR imaging algorithm, the paper discusses a new idea of SAR signalprocessing using the time-frequency characteristic of fractional Fourier transformcombining with SAR imaging algorithm to produce some new imaging characteristics.The main contents and innovative contributions of the paper are as follows:(1) On the basis of the analysis of the essential characteristic of SAR signal whichis range cell migration, several typical imaging algorithms are studied, which arerange-Doppler (R-D) algorithm, chirp-scaling (CS) algorithm and wave-numberdomain (WD) algorithm. Furthermore, R-D algorithm and CS algorithm under squintmode are studied.(2) On the basis of the research of the basic principle and properties of FRFT, thetime-frequency characteristic of the FRFT and its advantages in the processing ofchirp signal are introduced and the discrete algorithm is discussed in detail. Finally,the simulation verifies the good focusing performance of discrete algorithm of FRFTis superior to the traditional FFT, as a theoretical preparation for the study of imagingtechnology.(3) The Chirp-Scaling algorithm is an efficient imaging algorithm without theinterpolation, which uses FFT to get match filtering imaging from the echo Chirpsignal. Chirp is non-station signal, in order to better use its time-frequencycharacteristic, improving the imaging resolution and reducing the complexity of thealgorithm, this paper proposes a novel Chirp Scaling algorithm based on the FRFT(FRFT-CS). Simulation results show that the FRFT-CS algorithm is much simple inimplementation, higher resolution, and greater side-lobe reduction ratio.(4) A novel wave-number domain imaging algorithm based on the fractionalFourier transform (FRFT-RMA) is put forward. In which the Stolt interpolation isreplaced by the remaining phase compensation and FRFT, which are utilized to perform the bulk range cell migration correcting and the inverse Fourier Transform,hence the computational efficiency is improved significantly. On the other hand, theFRFT is applied to complete the remaining azimuth compression and the InverseFourier Transform, to achieve high resolution images for targets in radar imaging.The results of simulation show that the algorithm is much simple in implementation,and the efficiency and accuracy of the proposed method are much better thantraditional wave-number domain algorithm.