The effects of the backscattering enhancement on signals of rain radar

研究了毫米波下雨雷达信号的后向散射增强。这种效应很难在很小的反向角度内以高分辨率观察到。在30GHz波段进行了大球面散射体极化雷达参数的实验室测量，研究了入射偏振态对极化雷达参数的影响。实测的线和圆去极化比与理论计算结果吻合较好，表明圆极化由于多次散射而产生的交叉极化水平比线极化大得多。利用50GHz散射计对后向散射脉冲波进行了分析，以区分多重散射过程和接收到的脉冲形状。结果表明，散射过程可以被分离，时间分辨率为3 nsec。在利用机载雷达测量雨率时，雷达信号中包含了海面的回波。为了评价这一点，在实验室实验中检查了平坦边界和粗糙边界附近散射体的散射。边界表面粗糙度会影响接收到的脉冲形状，特别是在散射体与粗糙边界之间的二阶散射。

The backscattering enhancement in rain radar signals at millimeter waves was examined. This effect was difficult to observe with high resolution within a very small angle in the backward direction. Laboratory measurements of polarimetric radar parameters for large spherical scatterers were then performed at 30GHz to study the dependence on incidence polarization states. The measured linear and circular depolarization ratios were in good agreement with theoretical calculations, showing the cross-polar level of circular polarization due to multiple scattering is very large compared with that of linear polarization. The backscattered pulse wave using the 50GHz scatterometer was also analyzed to distinguish the multiple scattering process from the received pulse shape. The results indicated that the scattering process was confirmed to be separated with the time resolution of 3 nsec. In measuring the rain rate by the air-born radar, the echo from sea surfaces was included in radar signals. To evaluate this, the scattering.from scatterers near flat and rough boundaries was examined in laboratory experiments. The surface roughness of the boundaries was found to affect the received pulse shape, especially in the second order scattering between scatterers and rough boundary.