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本文给出了用三种频率(12.0,25.3和33.5GHz)的雨衰减值确定沿路径雨滴尺寸的分布的一种反演方法。描述了一条路径长度为1.26公里的微波、毫米波地面传输的实验系统。路径雨滴尺寸分布的反演方程是属于第一类Fredholm积分方程。其方程的核函数是含有前向散射函数因子的函数。文章通过计算机数值解求出了对应于上述三种频率的核函数。假定沿路径雨滴尺寸分布服从于指数模式N(D)=N_0e~(-AD),反演求解积分方程以获取模式中的参数N_0和A参数的最优化解。从大量的雨衰减实测数据用上述方法反演得到的沿路径雨滴尺寸分布的结果与著名的M—P雨滴尺寸分布十分接近。
In this paper, an inversion method for determining the distribution of raindrop size along a path is given using the attenuation values of rain attenuation at three frequencies (12.0, 25.3 and 33.5 GHz). An experimental system for microwave and millimeter wave ground transmission with a path length of 1.26 km is described. The inversion equations of the path raindrop size distribution belong to the first Fredholm integral equation. The kernel function of the equation is a function that contains the forward scatter function factor. The paper obtains the kernel function corresponding to the above three kinds of frequencies by computer numerical solution. Assuming that the raindrop size distribution along the path obeys the exponential model N (D) = N_0e ~ (-AD), the integral equation is solved inversely to obtain the optimal solution of the parameters N_0 and A in the model. The results of rainfall raindrop size distributions retrieved by the above method from a large number of rain attenuation measured data are in good agreement with the well-known M-P raindrop size distribution.