復(fù)雜運(yùn)動SAR回波模型與成像方法研究
[Abstract]:Synthetic Aperture Radar (SAR) (SAR) can generate high resolution microwave images of observation scenes under all illumination / weather conditions. Because the complex motion platform SAR uses fighter plane as the carrier and deviates from the ideal state of motion due to the external interference, the trajectory is 3D curve, so the traditional imaging algorithm is no longer applicable. Therefore, how to realize the complex motion platform SAR for high resolution imaging of observation scene needs to be studied urgently. In this paper, the SAR model of complex motion platform is established, and the difference between complex motion SAR and ideal motion SAR is analyzed in detail, as well as the complex motion imaging algorithm suitable for the case of small and large motion error. The main contents are divided into the following three parts: firstly, this paper analyzes the difference between SAR of complex motion and SAR of ideal motion from four aspects: motion error, phase error, Doppler parameter and azimuth resolution. The result shows that the azimuth echo signal is a nonlinear frequency modulated signal, and if the motion is not compensated, it will lead to the non-uniform sampling in the azimuth direction. In the aspect of phase error, the effect of phase error of different order on echo signal is analyzed. The theoretical azimuth resolution is redefined in the aspect of azimuth resolution: the main lobe-3dB width after pulse compression of azimuth echo signal. In terms of Doppler parameters, the acceleration tolerance of Doppler bandwidth broadening for complex motion SAR under different motion models is analyzed, and the void variation of complex motion Doppler history is also analyzed. It is concluded that SAR with complex motion needs to use BP algorithm to image the scene point by point. Then this paper introduces the complex motion imaging algorithm which is suitable for the case of small motion error: BP algorithm based on the measured data of IMU. The conclusion that Legendre orthogonal polynomial is the optimal basis function for high order fitting of the algorithm is obtained by imaging index, and then the tolerance of acceleration, velocity and position measurement error to ensure that the algorithm does not fail is obtained. This algorithm is only suitable for small measurement errors. When the measurement error is large, the BP algorithm based on echo data parameter estimation should be adopted. Finally, this paper introduces a complex motion imaging algorithm suitable for large motion errors: a BP algorithm based on phase tracking of strong point information based on inverse solution of Legendre coefficients. The influence of signal-clutter ratio on phase tracking algorithm is studied, and the threshold of signal-to-clutter ratio is obtained. The influence of the number of strong points and geometric distribution on the radar position is analyzed. Then by setting the appropriate signal to clutter ratio and the number of strong points and inverse solving the Legendre coefficient to obtain the oblique distance history of the radar platform, the phase compensation factor of the BP algorithm is constructed and applied to the scene imaging of the BP algorithm, which verifies the effectiveness of the algorithm.
【學(xué)位授予單位】:電子科技大學(xué)
【學(xué)位級別】:碩士
【學(xué)位授予年份】:2017
【分類號】:TN957.52
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