| Radar imaging has been the main trend of the development of radar. It has the characteristics of all-weather, day/night, long range and high-resolution. The key to Radar imaging technology is improving the imaging resolution. The basic principle is, achieving high range resolution by transmitting broadband signals, and achieving high cross-range resolution by the long linear array that formed by the radar platform motion.There are two major aspects of the development of Radar imaging. That is, Synthetic Aperture Radar (SAR) imaging and Inverse synthetic aperture radar (ISAR) imaging. Firstly, the fundamental theory of ISAR is discussed and the significance of the LFM (linear frequency modulated) signal and SFW (stepped frequency waveforms) is analyzed, which is used to improve the imaging resolution. For the characteristics of ship ISAR imaging, considering the structure of signal processing board, the software implementation of ISAR imaging system is introduced, meanwhile, the tasks dispatch and algorithm flow on DSP are analyzed in details. Secondly, the discussion of the fundamental theory of SAR is made, which is more mature in development. There are three types of SAR, such as striped SAR, spotlight SAR, scanning SAR. However, only the striped SAR is discussed. Based on the knowing the fundamental theory of striped SAR, both the striped SAR real-time imaging system and the DSP implementation of the SAR algorithm are introduced. As the key point of the implementation of SAR and ISAR is the part of signal processing, and the basic of this is DSP. The parameter index of the DSP chips is the bottleneck of improving the system performance. According to the implementation of imaging system, at last the TI's DSP of 8 cores TMS320C6678is chosen. Finally, the Multi-core structure of this DSP chip and multi-core multi-layer system on chip are introduced in details. The low-power and high performance of the multi-core DSP bring more room for improvement to Radar imaging system. |
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