In Synthetic Aperture Radar, Noise Equivalent Sigma Nought (NESZ) is usually verified by measurements over targets with ideally null backscatter, like calm water, or flat surfaces. This condition is quite different from the normal one, in term of quantization, source temperature, ambiguities and received signal energy. We propose a novel method based on interferometry that estimates NESZ in presence of a significant source backscatter. It exploits the principle that noise is the ultimate and unavoidable factor limiting coherence. For each value of backscatter (say in an histogram), a search is made for the target with highest coherence. NESZ is then estimated by fitting the theoretical model of coherence versus signal-to-noise-ratio. The estimate is performed for different range by exploiting narrow strips. The method relies on the existence of some target whose coherence is limited only by thermal noise. Results of processing Sentinel 1A / 1B data over the 'Salar de Uyuni' site are here compared with the classical measures over signal-free region.
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机译：在合成孔径雷达中，噪声等效西格玛诺特（NESZ）通常通过对具有理想零反向散射的目标（如平静的水面或平坦的表面）进行测量来验证。在量化，源温度，模糊度和接收信号能量方面，该条件与正常条件完全不同。我们提出了一种基于干涉测量的新颖方法，该方法可在存在重大源反向散射的情况下估算NESZ。它利用了噪声是限制相干性的最终且不可避免的因素这一原理。对于每个反向散射值（以直方图表示），将搜索具有最高相干性的目标。然后通过拟合相干性与信噪比的理论模型来估计NESZ。通过利用窄条对不同范围执行估计。该方法依赖于某些目标的存在，这些目标的相干性仅受热噪声限制。这里将在“ Salar de Uyuni”站点上处理Sentinel 1A / 1B数据的结果与在无信号区域上的经典测量结果进行比较。
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