Research On Ship SAR Imaging Algorithms Based On Parameter Estimation

Synthetic Aperture Radar(SAR)imaging has been widely used in civilian and military applications owing to its all-weather,all-day and high-resolution characteristics.In recent years,the detection and imaging technology of moving target has been an important branch of SAR imaging research.Based on the basic principles of SAR imaging,this paper introduces two classic SAR imaging algorithms,Range-Dopple(RD)algorithm and Chirp Scaling(CS)algorithm.Then,the SAR imaging of the moving targets is deeply studied by estimating the motion parameters of moving targets based on the time-frequency distribution of the moving targets.Finally,the rotating target is detected and analyzed,its rotational motion parameters are estimated.The main work includes the following aspects: 1.Analyzing the high-resolution principle of SAR imaging.In order to obtain high-quality target SAR image,the high resolution of distance and azimuth direction are obtained by matched filtering method and technique synthetic aperture technique,respectively.Then two common high-resolution SAR imaging algorithms are described: RD algorithm and CS algorithm.RD algorithm and CS algorithm are used to simulate the stationary targets respectively,the results obtained by these two imaging algorithms are compared.Subsequently,the electromagnetic scattering model of the target is studied,the electromagnetic scattering coefficient of the ship is calculated by GO-PO method.Based on the electromagnetic scattering model,the SAR algorithm is used to image the ship target.2.Studying the imaging of moving targets.Firstly,the SAR echo signal characteristics of moving targets are used to analyze the influence of moving parameters on Doppler parameters,then the effects of different motion parameters on SAR images are analyzed.According to the relationship between the Doppler centroid and the target range velocity,the Doppler centroid is estimated by the envelope alignment method,and the Doppler rate is estimated based on the RWT time-frequency transform method.Finally,based on the parameter estimation,the moving target SAR imaging algorithm is simulated for the moving target.3.Establishing the rotating target SAR echo model.According to the characteristics of the target rotation to sinusoidal modulation of the echo and the principle of paired echo,the typical characteristics of the target in the SAR image under different rotation parameters are analyzed.This provides a theoretical basis for identifying and detecting rotating targets in SAR images.Then,using the characteristics of the rotating target in the time-frequency domain,the separation and detection of the rotating target and the stationary target are realized.Based on the separated rotating target echo signal,a feasible parameter estimation method is proposed according to the characteristics of its echo signal.The target rotational motion parameters are estimated.