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Stored energies in electric and magnetic current densities for small antennas

Jonsson, Lars and Gustafsson, Mats LU (2015) In Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences 471(2176). p.1-23
Abstract
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... (More)
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. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
keywords
stored energy, antennas, polarizability tensors, Q-factor, physical bounds
in
Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences
volume
471
issue
2176
pages
1 - 23
publisher
Royal Society
external identifiers
  • scopus:84926303291
ISSN
1364-5021
DOI
10.1098/rspa.2014.0897
project
EIT_CACO-EMD Complex analysis and convex optimization for EM design
language
English
LU publication?
yes
id
f0be0a5e-07da-478a-8060-53d306f86b83 (old id 5205005)
date added to LUP
2015-03-30 12:59:33
date last changed
2017-09-10 04:50:33
@article{f0be0a5e-07da-478a-8060-53d306f86b83,
  abstract     = {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.},
  author       = {Jonsson, Lars and Gustafsson, Mats},
  issn         = {1364-5021},
  keyword      = {stored energy,antennas,polarizability tensors,Q-factor,physical bounds},
  language     = {eng},
  number       = {2176},
  pages        = {1--23},
  publisher    = {Royal Society},
  series       = {Royal Society of London. Proceedings A. Mathematical, Physical and Engineering Sciences},
  title        = {Stored energies in electric and magnetic current densities for small antennas},
  url          = {http://dx.doi.org/10.1098/rspa.2014.0897},
  volume       = {471},
  year         = {2015},
}