Research On Motion Compensation Of Airborne Synthetic Aperture Radar

Synthetic Aperture Radar (SAR) is one of the most advanced inventions in the 20th century. SAR has the all-weather, day/night capability to generate a high-resolution representation of the targets over a long range. With the technology and the economy development, SAR is more widely used on many fields such as military, agriculture, forestry, geology, and oceanography i.e..In concept, "Synthetic Aperture" means that correlative radar system and the motion of single antenna are used to simulate the function of a lot of actual antennae. SAR launches the electromagnetic wave to the target and acquires the orientation resolution of the target with the Doppler frequency shift theory.The opposite motion between the SAR flat and the imaging area is the sticking point in acquiring the high- resolution orientation imaging. As for airborne SAR, because of the random factors in the environment, the motion of the airplane inevitably produces the motion errors. This directly results in the phase errors of the radar signals, destroys the phase correlation and orientation resolution, and blurs the quality of the image. So it must compensate the motion errors in order to obtain the high-resolution image.Motion compensation is the important step in airborne SAR, which directly influences the image's quality. It includes many hardware and software technologies and is the hot point of SAR study in the world. Because the information of SAR cannot be acquired adequately, the study is very difficult. The author has made a wide and in-depth study on SAR technologies, and has ever gone to Shanxi Yanliang aerodrome and Hefei for the field survey of SAR. The thesis is also incorporated with the project of "Research on Application Of '3S' Integrated Technology in Radar" belonging to the 10th Five-year National Project.The thesis is composed of six chapters. Whereas the fact that imaging is the precondition of motion compensation, the imaging principal and several keytechnologies are discussed in the former section of the thesis. The third chapters analyses the motion errors' causes of the airplane flat, discusses the relationship of the motion errors and the phase errors and their influence to the imaging, and also exerts the power spectrum to define the precision requirement of motion compensation system. The forth chapter analyzes the moving sensors including Global Positioning System (GPS^ Inertial Navigation System (INS) and Inertial Measurement Unit (IMU), gives out the feature requirements of strapdown IMU, and analyzes the influences of INS/GPS combination to the attitude of the plane, gives the design of the motion compensation system. The fifth chapter makes the study of Phase Grade Autofocus (PGA) algorithm, gives out its diagram designing, makes the improving of the algorithm, and acquire the phase errors from the radar echo's data.The last chapter summarizes the content of the thesis and makes the prospect of the research. The thesis provides the important science foundations for the 2003 and 2004 flights trials of the project "Research on Application Of *3S' Integrated Technology in Radar".