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In order to achieve a high range resolution and low instantaneous bandwidth, stepped frequency synthetic aperture radar (SAR) is widely used with stepped-frequency chirps and frequency-domain spectrum reconstruction method. To combine the spectrum reconstruction with SAR image algorithms, “Image for each sub-band and then reconstruct the wideband spectrum” is a more adaptable flow since its validity for almost all imaging algorithms. However, due to the two-dimensional (2-D) spectrum twisting, a special problem called range spectrum aliasing may occur and lead the flow to invalidity, especially in high-resolution SAR systems. In this paper, we discuss the extended range spectrum by the analysis of the 2-D twisting spectrum, judge its influence through an azimuth threshold resolution, and propose an improved stepped-frequency SAR imaging algorithm with the range spectral-length extension (RSLE) strategy, which can eliminate the range spectrum aliasing. After theoretic analyses, simulations and experimental results are provided to demonstrate the proposed algorithm.
Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of (Volume:5 , Issue: 5 )
Date of Publication: Oct. 2012