Real-time Synchronous Orbit SAR Imaging Algorithm

Spaceborne synthetic aperture radar with uninterrupted observation of the surface,is not affected by factors such as cloud cover and luminosity, so widely used ingeomorphological mapping, resource exploration and military reconnaissance and otherareas. Currently existing spaceborne SAR mainly low orbit, but its smaller swath, revisitcycle is short. Especially now that the development of high-altitude weapons, making itless secure, more suited to the needs of modern warfare. However GEOSAR is a goodsolution to this problem.This paper mainly GEOSAR real-time imaging algorithm analysis and research forGEOSAR IF echo processing and analysis. The main contents are as follows:(1): Digital signal processing platform for TS201introduced as ADI’s high-endDSP signal chip, which has a powerful floating-point computing power. Combined withVisual DSP5.0++simulation software, the algorithm accuracy and timeliness can beevaluated.(2):A detailed analysis of the characteristics of GEOSAR orbit. GEOSARestablished track model to study the characteristics of the velocity of the satellite, thebeam scanning speed and run track and so on. Since the image forming process, thecharacteristics of large Doppler radar, so focused on the Doppler characteristics of thesatellite, while the influence of Doppler parameters for the attitude error, the article alsogives the simulation data, the imaging algorithm provide some reference.(3):Detailed theoretical basis and engineering applications of digitaldown-conversion technology. IF echo data sampling rate is generally relatively large, isnot conducive to real-time image processing algorithms, digital down conversion can bea good solution to this problem, ensure that the signal bandwidth, the decimation filter.Detailed analysis of the characteristics of the CIC filter, which can improve themulti-stage cascaded CIC stopband attenuation characteristics, in addition to the limitedcapacity for processing DSP chip, multi-chip DSP mode using pipeline processing,improved signal processing front.(4): Study of two-dimensional spectral characteristics GEOSAR. An improved RDsignal processing algorithms were carried out on the range and azimuth pulsecompression analysis, and in order to increase the side-lobe attenuation, signal analysis of the main lobe of the impact of different windowing Finally GEOSAR point targetimaging.