Multiple Scattering Effects of Electromagnetic Waves from Randomly Distributed Particles and Its Application to a High Precision Radar

随机分布粒子电磁波的多重散射效应及其在高精度雷达中的应用

基本信息

批准号：
08650515
负责人：
ITO Shigeo
金额：
$ 1.41万
依托单位：
Toyo University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-08650515/
关键词：
RANDOM MEDIA RADAR ELECTROMAGNETIC SCATTERING RAIN MILLIMETER WAVES MULTIPLE SCATTERING PROPAGATION 降雨散乱

项目摘要

For millimeter wave regions, the effects of multiple scattering in rain on radar signals may not be ignored for higher frequencies or higher rainfall rates. The theoretical estimation of rainfall rate has been based on the conventional polarimetric radar equation, which only takes account of the first-order scattering contribution. However, air-borne radar measurements of rain have shown very high depolarization ratios at 34.5GHz and suggested that the multiple scattering is included. The purpose of this paper is to clarify the effects of multiple scattering on radar signals in the time domain and to apply to the development of the radar systems with higher precision. To examine multiple scattering effects, the second-order solution of the radiative transfer equation was derived for the linearly polarized incident waves. Both of co-polarized and cross-polarized intensities were calculated. The theoretical results indicate a slower decrease in the co-polarized intensity against the range from the radar and a rapid increase in the linear depolarization ratio (LDR) near the rear edge of the rain layr. The laboratory measurements under controlled scattering parameters were made for simulated rain of randomly distributed spherical scatterers at 16.5GHz and 30GHz. The measured LDR is very large and is in remarkably good agreement with theoretical calculations. Therefore, the conventional radar equation may overestimate the rainfall rates in view of the present analysis. The simultaneous observation of co-and corss-polarized intensity would lead to estimate the higher precise rainfall rate and would need to analyze the fine structure of rain. We will further examine an alternative approximate solution of the radiative transfer equation and consider to treat the case of the nonspherical raindrops. The similar experiment should be done for various kind of size parameters of the raindrops.

对于毫米波区域，对于较高的频率或更高的降雨速率，可能不会忽略雨中多个散射对雷达信号的影响。降雨速率的理论估计是基于常规的极化雷达方程，该方程仅考虑一阶散射贡献。但是，雨水的空气雷达测量值显示在34.5GHz时表现出很高的去极化比，并建议包括多个散射。本文的目的是阐明多个散射对时间域中雷达信号的影响，并应用于具有更高精度的雷达系统的开发。为了检查多个散射效应，为线性极化的入射波得出了辐射转移方程的二阶解。计算了共偏解式和交叉极化强度。理论结果表明，与雷达相对于雷达的范围以及在雨layr后边缘附近的线性去极化比（LDR）迅速增加的范围降低了降低。对受控散射参数下的实验室测量进行了测量，以模拟在16.5GHz和30GHz处随机分布的球形散射器的模拟降雨。测得的LDR非常大，并且与理论计算非常吻合。因此，鉴于目前的分析，常规雷达方程可能高估了降雨速率。同时观察共同和CORSS极度强度将导致估计更高的精确降雨率，并且需要分析雨水的良好结构。我们将进一步检查辐射转移方程的替代近似解，并考虑处理非球雨滴的情况。对于雨滴的各种大小参数，应进行类似的实验。