Research On Parameter Estimation Technologies Of Distributed SAR Moving Targets

Spaceborne synthetic aperture radar (SAR) system has a strong hidden ability, and the detection distance is long. It can effectively improve the survival and Combating capability in the modern electronic and information warfare environment. Therefore the use of this system in the parameter estimation is becoming an increasingly important part of military technology. This thesis deals with spaceborne synthetic aperture radar systems. This thesis studies the multi-platform of slow and fast moving targets parameter estimation technology. In the process of synthetic aperture radar imaging, moving target occurs not only in the azimuth shifting, but also the image is defocused. As a result, an accurate estimate of the moving parameters of moving targets is the key to the moving target precise imaging. In the modern war, multiple moving targets exist in the synthetic aperture. It's really difficult to distinguish the targets and parameter estimation accuracy is not high. So we must find the right methods to accurately estimate the parameters of the moving targets. The main content and innovation are as follows:1) When there are multiple moving targets in a SAR Synthetic Aperture within the same time, because of their similar chirp rates, using the traditional method of parameter estimation is difficult to identify them and the estimation accuracy is poor. Moving targets'parameter estimation is a key problem of SAR. A method of Hilbert Huang Transform- Wigner Ville Distribution (HHT-WVD) is proposed, which solves the problems of the WVD cross-terms and the HHT low time-frequency clustering. It achieves the accurate estimation of the multiple moving targets'Doppler parameters in the SAR Synthetic Aperture. Simulation results show that this algorithm can identify multiple moving targets, and it has a high accuracy of parameter estimation and low computation complexity. So it is worthy to be applied widely in practice.2) To estimate the ground targets'azimuth speed which is coupled with spaceborne distributed synthetic aperture radar', the Fractional Fourier Transform (FrFT)-Multiple Signal Classification (MUSIC) space-time-frequency algorithm is proposed. Firstly, make fusion with space-time-frequency distribution matrix formed by Fractional Fourier transform. Then, use this distribution matrix instead of the traditional MUSIC covariance matrix to construct FrFT- MUSIC spectral function. Target speed is estimated by searching. Simulation results show that this algorithm has a high accuracy of parameter estimation and strong resistance to noise, there is no blind speed.3) Deal with the problem of multiple high-speed moving targets parameter estimation in the synthetic aperture radar system. Based on the accurate estimation parameter principles, we study the range cell migration correction and space-time-frequency algorithms. In range cell migration correction (RCMC), the paper discovers that spectrum splitting influences the procedure of RCMC. After studying it, the paper gives correction method based on frequency transformation, and simulation results show that this algorithm has a high accuracy.