On the EM Degrees of Freedom in Scattering Environments
On the EM Degrees of Freedom in Scattering Environments
复制标题
散射环境中的电磁自由度
DOI：
10.1109/tap.2011.2163776
复制
发表时间：
2011
影响因子：
5.7
通讯作者：
R. Janaswamy
中科院分区：
文献类型：
--
作者：
R. Janaswamy
通过考虑在理想导体圆柱体存在下的线源辐射的二维问题，并将真实的功率流分解到将发射节点与接收节点分开的外接观测圆上，导出了相互通信的节点网络在散射环境中的电磁自由度的简单公式。假设线源的位置、幅度和相位是独立同分布的（i.i.d.）随机变量类似地，假设观察圆外区域中的散射体的位置为独立同分布。随机变量精确的散射问题被转换成积分方程的形式，其中散射电流密度的傅立叶系数是未知数。基于玻恩近似，这是有效的轻度散射密度和渐近分析，推导出一个封闭的形式表示的自由度的散射环境中的数量。观察近场的自由度的测定的好处包括在考虑的数值例子。如果每个源的功率和/或外切圆内的源的数量被制成代数地随着圆的大小而增加，则表明散射环境可以提供比自由空间中可用的自由度高得多的自由度。
By considering the 2D problem of electrical line sources radiating in the presence of perfectly conducting cylinders and decomposing the real power flow on a circumscribing observation circle separating the transmit nodes from the receive nodes, simple formulas are derived for the electromagnetic degrees of freedom in scattering environments for a network of nodes communicating with each other. The locations, magnitudes, and phases of the line sources are assumed to be independent and identically distributed (i.i.d.) random variables. Similarly, the locations of the scatterers in the region outside the observation circle are assumed to be i.i.d. random variables. The exact scattering problem is cast in the form of an integral equation, where the Fourier coefficients of the scatter current density are the unknowns. Based on the Born approximation that is valid for mild scatter densities and asymptotic analysis, a closed form expression is derived for the number of degrees of freedom in scattering environments. The benefit of observing near-fields in the determination of degrees of freedom is included in the numerical examples considered. If the power per source and/or the number of sources within the circumscribing circle are made to increase algebraically with the size of the circle, it is shown that scattering environments can offer much higher degrees of freedom than what are available in free-space.