The Information Carried by Scattered Waves: Near-Field and Nonasymptotic Regimes
The Information Carried by Scattered Waves: Near-Field and Nonasymptotic Regimes
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散射波携带的信息：近场和非渐近状态
DOI：
10.1109/tap.2015.2429742
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发表时间：
2015
影响因子：
5.7
通讯作者：
F. Schettino
中科院分区：
文献类型：
--
作者：
M. Franceschetti;M. Migliore;Paolo Minero;F. Schettino
确定了由时间谐波、任意平方可积电流密度和散射元素的随机分布的存在下在二维设置中辐射的场的空间自由度的数量。它示出，与近场的第k奇异值在存在的散射体外部的切割呈现出一个沉重的尾巴衰减作为其指数的函数，而不是通常的指数衰减发生在自由空间中观察到的一个临界指数项之外的有功功率。这种近场信息增益由于散射最近预期Janaswamy使用随机源模型，它在这里扩展到任意源，它被证明在大型辐射系统的极限消失。它还表明，相同的信息增益和渐近截止发生的奇异值的字段辐射在自由空间中。总的来说，这些结果表明，虽然存在的散射体外部的削减可以增加信道的数量，可以利用通信的有功功率在近场，他们不改变信道的数量相关联的字段，也不渐近行为的自由度的数量。
The number of spatial degrees of freedom of the field radiated in a two-dimensional setting by a time-harmonic, arbitrary square-integrable current density and in the presence of a random distribution of scattering elements is determined. It is shown that the active power associated to the kth singular value of the near field in the presence of scatterers external to the cut presents a heavy tail decay as a function of its index, rather than the usual exponential attenuation occurring beyond a critical index term observed in free space. This near-field information gain due to scattering was recently anticipated by Janaswamy using a stochastic source model, it is extended here to arbitrary sources, and it is shown to disappear in the limit of large radiating systems. It is also shown that the same information gain and asymptotic cut-off occurs for the singular values of the field radiating in free space. Collectively, these results show that while the presence of scatterers external to the cut can increase the number of channels that can be exploited for communication by the active power in the near field, they do not change the number of channels associated to the field, nor the asymptotic behavior of the number of degrees of freedom.