Spaceborne SAR Imaging Using Range-Doppler Alrorithm

Synthetic aperture radar (SAR) imaging technique is related with electronic engineering, computer science and digital signal processing. The appearing and development of SAR enlarge the traditional radars'application. As a high resolution microwave instrument, it has ability of large planetary image areas in all weather during day and night and has to a thing some wear deeply ability. With the development of SAR imaging quality, high range and azimuth resolution has come true. As a result, SAR has been an important tool for scientific research and remote sensing. It will take on a supreme in both military and civil.It can improve the resolution of range and azimuth by impulse compression technology and synthesizing a large aperture respectively, and then it can obtain the planar high-resolution image of the object being observed. It is the most prominent technique characteristic and kernel of SAR. The Doppler history of spaceborne SAR is determined by two Doppler parameters. These two parameters play a key role in azimuth processing of spaceborne SAR.Firstly, we offer a brief account of the development history, the technology characteristics and basic principles of Spaceborne SAR in its part, and go over the basic theory of SAR making a theoretical preparation for following chapters, introducing the principle of SAR, range and azimuth resolution, principle of the stationary phase.We focus on studying the Range Doppler algorithm for spaceborne SAR imaging processing, the reason of range migration. Because the Doppler history of spaceborne SAR is determined by two Doppler parameters, these two parameters play a key role in azimuth processing of spaceborne SAR. So the Doppler frequency rate needs to be estimated from the raw echo data in order to focus in azimuth commendably. In the following parts, the dissertation gives some methods to estimate Doppler parameters. At the Doppler centroid aspect, this dissertation makes use of Maximum value method and Energy method to estimate Doppler centroid. At the Doppler frequency aspect, this paper makes use of Time-frequency method. Thus the echo model, we obtained the spot model by using Range-Doppler algorithm.Finally, the experiments are performed using Radarsat and ERS raw data images acquired by R-D algorithm, then, we estimate the Doppler parameters of Radarsat raw data, and the results are carefully analysis. Results show that the inversion method in this dissertation is valid and accurate to certain extent.