基于1–10GHz空地链路信号的雨强监测方法可行性研究

空地链路上的微波信号受降雨影响, 会产生功率衰减和去极化效应. 基于这些物理特性, 本文提出利用1–10 GHz空地链路信号的降雨干扰项获取雨强的方法, 并开展了相关理论研究. 根据空地链路信号与雨滴复杂的相互作用, 研究了空地链路信号频率为1–10 GHz时, 雨强 (rain rate, R) 对衰减 (attenuation, A) 和交叉极化分辨率 (cross-polarization discrimination, XPD)的影响, 分别建立了A-R和XPD-R关系模型. 通过数值模拟, 分别分析了利用上述两个关系模型估测雨强的可行性, 并系统研究了不同频率、极化方式和仰角条件下的适用性. 研究结果表明, 对于水平极化或圆极化, 且频率较高的空地链路信号, 利用A-R关系反演强降雨具有理论上的可行性; 对于不同频率和极化方式的信号, XPD-R关系模型都可以用于反演雨强, 并且对于1–50 mm·h^-1范围内的雨强, XPD较为敏感; 不同仰角条件下, A-R和XPD-R 模型都适用. 在4–10 GHz时, 本文的XPD-R模型和国际电信联盟ITU-R中XPD预测模型的结果非常接近. 所得出的结论对于下一步开展相关的验证实验, 拓展卫星系统的气象应用, 实时估测降雨强度, 实现全球降雨观测具有重要的参考价值. 关键词： 空地链路信号 雨强 衰减特性 交叉极化分辨率(XPD)

Feasibility research on the method of rain rate detection based on space-earth link signals at 1-10 GHz

Satellite signals across the space-earth link are always seriously affected by rain, inducing attenuation and depolarization. In this paper, two methods of estimating the rain rate are investigated based on the space-earth link signals in a frequency range of 1–10 GHz. Firstly, the effects of rain rate (R) on attenuation (A) and cross-polarization discrimination (XPD) are studied, according to the complex interaction between signals and raindrops. Then, two relevant models A-R and XPD-R are established, which are the key techniques to estimate the rain rate. The feasibilities of the above models are analyzed. In addition, their applicabilities at various frequencies, polarization and satellite elevations are also investigated systematically. The results show that for the space-earth link signal with horizontal or circular polarization and higher frequency, the A-R relation can be used to estimate the heavy rain; for signals with different frequencies and polarizations, XPD-R is suited to estimate various rain rates, especially in a frequency range of 1–50 mm·h^-1; A-R and XPD-R are both applicable at different elevations. Moreover, the XPD-R relation is consistent with the prediction model of XPD proposed by ITU at 4–10 GHz. The results obtained in this work will play an important role in the future verification experiment, the nowcasting automatic detection of rain rate and global rain observations.
Keywords： space-earth link signals rain rate attenuation characteristic cross-polarization discrimination (XPD)