Introduction to Synthetic Aperture Radar (SAR)

摘要

The synthetic aperture radar principle has been discovered in the early 50th. Since then, a rapid development took place all over the world and a couple of air- and space-borne systems are operational today. Progress made in technology and digital signal processing lead to very flexible systems useful for military and civilian applications. Radar has proved to be valuable before, because of its day-and-night capability and the possibility to penetrate clouds and rain. Optical instruments however had great advantages in the interpretation of depicted objects. The great wavelength of radar signals limits the achievable resolution in cross range direction of real aperture radar systems. Thus, imaging cannot be realized using static radar systems. The idea of SAR was to transmit pulses and store the scene echoes along a synthetic aperture (i.e. the path of the SAR sensor) and to combine the echoes afterwards by the application of an appropriate focusing algorithm. The combination is carried out coherently. As we will see, it is quit easy to understand the basic idea of SAR. We will show also the hardware concept or a SAR system and give an idea for a processing algorithm.