Stored energies in electric and magnetic current densities for small antennas
Stored energies in electric and magnetic current densities for small antennas
复制标题
以电流密度和磁流密度存储小型天线的能量
DOI：
10.1098/rspa.2014.0897
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
M. Gustafsson
中科院分区：
文献类型：
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作者：
B. Jonsson;M. Gustafsson
对于任意形状的结构，电流和磁流对于描述电磁存储能量以及相关天线Q和天线Q比的部分方向性D/Q是必不可少的。以前的D/Q结果的上限为天线建模的电流是足够准确的预测。这促使我们开发所需的分析，以确定上限和/或下限的电磁问题，包括磁模型电流。在这里，我们推导出新的表达式的存储能量，这是用来确定天线的Q界和D/Q界的组合的电流和磁电流，在电小天线的限制。在这项调查中，我们展示了新的分析结果，我们说明他们的数值实现。我们表明，天线Q的下限是成反比的最大特征值的某些组合的电和磁极化张量。这些结果是作为特例的纯电流的推广。所提出的方法来确定最小Q值，这是基于新的表达式的存储能量，也产生了一个家庭的电流密度最小化的最佳电流和磁电流，可以洞察天线设计。
Electric and magnetic currents are essential to describe electromagnetic-stored energy, and the associated antenna Q and the partial directivity to antenna Q-ratio, D/Q, for arbitrarily shaped structures. The upper bound of previous D/Q results for antennas modelled by electric currents is accurate enough to be predictive. This motivates us to develop the analysis required to determine upper and/or lower bounds for electromagnetic problems that include magnetic model currents. Here we derive new expressions for the stored energies, which are used to determine antenna Q bounds and D/Q bounds for the combination of electric and magnetic currents, in the limit of electrically small antennas. In this investigation, we show both new analytical results and we illustrate numerical realizations of them. We show that the lower bound of antenna Q is inversely proportional to the largest eigenvalue of certain combinations of the electric and magnetic polarizability tensors. These results are an extension of the electric only currents, which come as a special case. The proposed method to determine the minimum Q-value which is based on the new expressions for the stored energies, also yields a family of current-density minimizers for optimal electric and magnetic currents that can lend insight into antenna designs.