Researches On Digital Synthetic Aperture Radar Technologies

Synthetic aperture radar is the high technology radar that can take high resolution imaging for the ground target by using the synthetic aperture principle and pulse compression technique. Synthetic aperture radar has been widely applied in the areas of military and civil and it has brought great benefits in economics and society. With the technology evolution and the application extension, people desire to get high quality synthetic aperture radar imaging, not only require the single frequency band, single mode high resolution imaging but also require multiple frequency bands, multiple modes high resolution imaging, and not only get the high resolution two-dimensional image of the ground immobile targets and moving targets but also get the three dimensional image of them, and not only require the side-looking high resolution synthetic aperture radar imaging but also require the squint or the forward-looking synthetic aperture radar imaging. So synthetic aperture radar is greater flexible high resolution imaging radar with multiple frequency bands, multiple polarizations, and multiple modes in the near future.For the request of multiple frequency bands, multiple polarizations, and multiple modes, the conventional synthetic aperture radar system needs to be developed by adopting the advanced radar architecture to improve the flexibility of synthetic aperture radar imaging system. The digital synthetic aperture radar technologies are the inevitable trend.The flexibility of synthetic aperture radar can be improved by implementing the digital techniques. The techniques can accomplish the rearrangement of some modules, which contributes new functions for the older synthetic aperture radar system. The developmental cost is saved, meanwhile, the system redundance is enhanced, which improves the reliability of synthetic aperture radar. Besides, the synthetic aperture radar functions can be implemented by software and the software extent can be improved on the basis of its digitalization, which implements the minitype and intellectualization of synthetic aperture radar.In the dissertation, the architecture of synthetic'aperture radar image processingsystem is analyzed, and the digital synthetic aperture radar technique is investigated from some key aspects in-detail-depth, and the digital synthetic radar receiving experimental platform is designed and implemented. The highlight contents are as follows:(1) Based on the architecture concept, researches on digital synthetic aperture radar technologies are made from functions, components and design rules. For the programmable requirements, a digital synthetic aperture radar architecture based on BUS is proposed. For the real-time processing requirements, the resources requirements of digital synthetic aperture radar real-time processing are analyzed quantitively. A processing structure based on multiple instructions multiple data and multiple instructions multiple data is proposed.(2) Researches on the direct digital synthesizing techniques of wide-band linear modulation frequency signal of digital synthetic aperture radar are made, and the experimental system for programmable synthesizing wide band linear modulation frequency signal based on AD9854 is complemented.(3) Researches on direct radio frequency sampling and digital quadrature modulation of digital SAR are made, especially digital product detection .method. For the imbalance of I/Q channel in digital product detection, the poly-phase filter is proposed.(4) Researches on two-dimensional auto gain controlling technique of digital synthetic aperture radar are made.(5) A receiving experimental platform based on universal workstation of digital synthetic aperture radar is developed. This platform can implement the programmable sample, implement programmable single and double channel mode, and implement quadurature modulation by software. So the system has the basic characteristics of the "software receiver".