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Fundamental Study on Sensing of Targets in Random Media

随机介质中目标感知的基础研究

基本信息

批准号：
05452223
负责人：
YOSHITOMI Kuniaki
金额：
$ 4.93万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

A method is presented for analyzing wave scattering of a conducting target in a random medium as a boundary value problem. The problem of the wave scattering can generally be formulated by introducing two operators : a Green's function in a random medium and a current generator, a new idea, which transforms any incident wave into a surface current on the target. The current generator depends on the target only and is mathematically constructed by Yasuura's method. The rader cross-section (RCS) of the target is expressed in terms of the current generator and the moment of the Green's function. The moment is approximately given as a solution of the moment equation in a random medium.The RCS of a conducting circular cylinder and elliptic cylinder in a strong turbulent medium where an incident wave becomes incoherent on the cylinder are numerically analyzed by a high-speed computer, and the characteristics of RCS are made clear for a conducting convex cylinder. As compared with the RCS of … More the cylinder in free space (sigma_0), the RCS in the turbulent medium (sigma_0) changes largely as a function of the spatial coherence length of the incident wave (L), the length of the axis transverse to the direction of incidence (d), the curvature of the cylinder surface directly illuminated by the incident wave, and the polarization of the incident wave : E-and H-waves. The change of sigma is summarized as follows : (1) For L*d, we have sigma*2sigma_0. (2) For L*d, sigma*2sigma_0 for E-wave incidence ; and the sigma for H-wave incidence changes largely, depending on the curvature of the cylinder, because of the creeping current on the cross-section surface. (3) For L<d, when the curvature changes rapidly, we have sigma_0<sigma*2sigma_0 for E-wave incidence and sigma*3sigma_0 in a case for H-wave incidence. When the curvature becomes flat, we have sigma*sigma_0 in some cases and sigma<sigma_0 in a case, for E-wave incidence, and sigma*0.5sigma_0 in a case for H-wave incidence. For L<d, we need to estimate the sigma in any cases carefully by our method. Less

提出了一种将随机介质中导电目标的波散射作为边值问题进行分析的方法。波散射问题通常可以通过引入两个算子来表述：随机介质中的格林函数和电流发生器，这是一种新的想法，它将任何入射波转换为目标上的表面电流。电流发生器仅取决于目标，并通过 Yasuura 方法进行数学构造。目标的雷达横截面（RCS）用电流发生器和格林函数的矩来表示。力矩近似地给出了随机介质中力矩方程的解。利用高速计算机对入射波在圆柱体上发生非相干的强湍流介质中的导电圆柱体和椭圆柱体的RCS进行了数值分析，明确了导电凸圆柱体的RCS特性。与自由空间中圆柱体的 RCS (sigma_0) 相比，湍流介质中的 RCS (sigma_0) 随着入射波的空间相干长度 (L)、垂直于入射方向的轴长度 (d)、入射波直接照射的圆柱体表面的曲率以及入射波的偏振（E 波和 H 波）而发生很大变化。 sigma 的变化总结如下： (1) 对于 L*d，我们有 sigma*2sigma_0。 (2) 对于L*d，E波入射为sigma*2sigma_0；由于横截面上存在蠕变电流，H 波入射的西格玛会根据圆柱体的曲率发生很大变化。 (3) 对于L<d，当曲率快速变化时，对于E波入射，我们有sigma_0<sigma*2sigma_0；对于H波入射，我们有sigma*3sigma_0。当曲率变得平坦时，对于 E 波入射，在某些情况下我们有 sigma*sigma_0，在某些情况下有 sigma<sigma_0，在 H 波入射情况下有 sigma*0.5sigma_0。对于 L<d，我们需要通过我们的方法仔细估计任何情况下的 sigma。较少的