Study Of SAR Imaging Algorithm Based On Scattering Model

Based on electromagnetic scattering model, conducting SAR imaging algorithm and its simulation can not only remedy the limitation of the SAR system in real scenes, which cannot obtain the measurement results, caused by various restrictions, but also provide effective method and more source images for imagery interpretation and target classification and recognition. The interaction between electromagnetic wave and the target can be better understood, which promotes the research of the method of target scattering feature extraction, by means of the research of electromagnetic scattering mechanism of SAR imaging simulation.Three classical SAR imaging algorithms are emphatically discussed, which are RangeDoppler algorithm, Chirp Scaling and Back Projection algorithms, based on the principle of SAR imaging. The SAR imaging simulation of stationary targets and moving targets are conducted on side-looking and squint cases. At last, the preliminary research on SAR imaging of the dynamic sea is done. This thesis mainly contains the following aspects:Firstly, based on the theory of SAR imaging, the principle of high resolution and the selection of imaging plane are discussed in detail. The Range-Doppler algorithm, the Chirp Scaling algorithm and the Back Projection algorithm are studied deeply. On the basis of the different way of range migration correction, the SAR images of the spactial point targets on sidelooking and squint cases are emulated respectively by different algorithms, which are compared between each other.Secondly, the study of SAR imaging algorithm based on scattering model is carried out in detail, which is followed by the calculation of the radar cross section of the target using the Gordon formal for Physical Optics. Then, some images of simple and complex targets are given out in this thesis, which verifies the effectiveness of the imaging algorithm. After that, the speckle noise of SAR images is removed by adding window filter, which makes the images much easier to identify.Thirdly, because of the phenomenon of SAR image shifting and defocusing due to target movement, the stationary targets imaging method cannot be applied for the moving targets.The key to moving targets imaging is the calculation of doppler parameters. The echo signal characteristics of the moving targets is analyzed detailly and the influence of motion parameters on the doppler parameters is discussed. In this thesis, the images of point targets and complex targets with different velocity and accelerated velocity are simulated by the method of moving target imaging algorithm, which verifies the effectiveness of the moving target imaging algorithm further. In the end, after analysing the properties of the sea surface movement, this thesis makes a preliminary study on the sea surface SAR imaging based on the moving target imaging algorithm. And the effect of the length of time accumulation on sea surface imaging is discussed.