Novel calibration method for emissivity measurement of radiometer calibration load
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摘要: 针对用于风云系列卫星有效载荷微波辐射计的地面定标的定标源的双站测量系统进行建模,引入与待测的有限大周期方锥阵列定标源结构一致的锥形阵列金属标定体(标定锥),取代常规的标定金属平板(标定板).通过基于三维时域有限差分(FDTD,Finite-Difference Time-Domain)算法和等效时谐场外推理论的仿真,结果显示标定锥具有与定标源相似的散射分布特性,并通过基于天线近场耦合理论的分析,标定锥与定标源具有相近的天线耦合功率密度分布,因此,用标定锥作为标定体可有效地消减由天线口面带来的近场天线耦合的误差.对于文中给定的定标源模型,在不考虑收发天线直接耦合的条件下,采用标定锥取代标定板进行标定可以将定标源发射率的测量精度提高一个数量级.Abstract: A novel bistatic measurement for calibration load used in prelaunch calibration for microwave radiometer carried on the Feng-Yun series satellite was preposed. The pyramidal metal calibration target which has the same structure to the periodic calibration load to be measured was introduced. Based on the three-dimension finite-difference time-domain (FDTD) method with perfectly matched layer (PML), the simulation results indicate that the novel calibration target has similar characteristics with the calibration load, and the power density distribution coupled by the horn antenna with a lens are also similar with each other, therefore using the pyramidal metal array can reduce the error caused by the antenna coupling. For the given calibration load, by taking the pyramidal metal array instead of the metal plane as the calibration target, an improvement of one order of magnitude will be achieved without considering the direct coupling between the transmitting and receiving antennas.
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Key words:
- calibration /
- radiometers /
- microwave measurement /
- remote sensing
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