Abstract
Range ambiguity is one of the factors which affect the SAR image quality. Alternately transmitting up and down chirp modulation pulses is one of the methods used to suppress the range ambiguity. However, the defocusing range ambiguous signal can still hold the stronger backscattering intensity than the mainlobe imaging area in some case, which has a severe impact on visual effects and subsequent applications. In this paper, a novel hybrid range ambiguity suppression method for up and down chirp modulation is proposed. The method can obtain the ambiguity area image and reduce the ambiguity signal power appropriately, by applying pulse compression using a contrary modulation rate and CFAR detecting method. The effectiveness and correctness of the approach is demonstrated by processing the archive images acquired by Chinese Gaofen-3 SAR sensor in full-polarization mode.
Highlights
In Synthetic Aperture Radar (SAR) imaging, range ambiguity is caused by the echoes of the previous and latter transmitted pulses scattered from undesired range zones [1]
Due to the contrary modulation rate to the main signals with odd ambiguous number, the method method of alternating up and down chirp modulation is provided with lower ambiguous signal of alternating up and down chirp modulation is provided with lower ambiguous signal power power owing to the defocusing of mismatched range filter
We have proposed a new range ambiguity suppression method for up and down chirp modulation
Summary
In Synthetic Aperture Radar (SAR) imaging, range ambiguity is caused by the echoes of the previous and latter transmitted pulses scattered from undesired range zones [1]. The others are algorithms which aim to disperse the peak ambiguous energy to reduce the impaction of ambiguity, for example, the finite depth of focus algorithm which automatically defocuses the range ambiguities, thereby reducing their peak levels [10,11], and more commonly modulation of successively transmitted pulses by alternating up and down chirps which spreads the ambiguities in the range direction [12,13]. This technique significantly reduces the ambiguity peaks and performs well for multi-polarization spaceborne SAR where a serious.
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