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Degrees of Freedom and Characteristic Modes : Estimates for radiating and arbitrarily shaped objects

Gustafsson, Mats LU orcid and Lundgren, Johan LU (2024) In IEEE Antennas and Propagation Magazine 66(6). p.18-28
Abstract

The number of degrees of freedom is a crucial parameter in many electromagnetic problems. In for example modern communication systems spatial diversity is often employed through multiple beams to enhance capacity and reliability. However, while the degrees of freedom can be computed, their connection to physical quantities is not as easily understood. To address this issue, this paper proposes a scattering-based formulation of characteristic mode analysis that can estimate the degrees of freedom of arbitrarily-shaped radiating objects. The relation between the number of dominant characteristic modes and physical characteristics differs for electrically large and small objects. Specifically, for large objects, it is connected to the mean... (More)

The number of degrees of freedom is a crucial parameter in many electromagnetic problems. In for example modern communication systems spatial diversity is often employed through multiple beams to enhance capacity and reliability. However, while the degrees of freedom can be computed, their connection to physical quantities is not as easily understood. To address this issue, this paper proposes a scattering-based formulation of characteristic mode analysis that can estimate the degrees of freedom of arbitrarily-shaped radiating objects. The relation between the number of dominant characteristic modes and physical characteristics differs for electrically large and small objects. Specifically, for large objects, it is connected to the mean shadow area, while for small objects, it is linked to their average polarizability through the forward scattering sum rule. Therefore, the average shadow area and polarizability are fundamental parameters that provide insight into the number of degrees of freedom for any object. These basic parameters also provide straightforward estimates of the minimum size of a device region required to support a desired number of electromagnetic degrees of freedom across a given spectral response.

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author
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type
Contribution to journal
publication status
published
subject
in
IEEE Antennas and Propagation Magazine
volume
66
issue
6
pages
11 pages
publisher
IEEE Computer Society
external identifiers
  • scopus:85192640233
ISSN
1045-9243
DOI
10.1109/MAP.2024.3389451
language
English
LU publication?
yes
id
15a430b1-88ae-4d17-ba6d-ca5aa8c0d77f
date added to LUP
2025-01-15 15:13:44
date last changed
2025-04-04 13:57:40
@article{15a430b1-88ae-4d17-ba6d-ca5aa8c0d77f,
  abstract     = {{<p>The number of degrees of freedom is a crucial parameter in many electromagnetic problems. In for example modern communication systems spatial diversity is often employed through multiple beams to enhance capacity and reliability. However, while the degrees of freedom can be computed, their connection to physical quantities is not as easily understood. To address this issue, this paper proposes a scattering-based formulation of characteristic mode analysis that can estimate the degrees of freedom of arbitrarily-shaped radiating objects. The relation between the number of dominant characteristic modes and physical characteristics differs for electrically large and small objects. Specifically, for large objects, it is connected to the mean shadow area, while for small objects, it is linked to their average polarizability through the forward scattering sum rule. Therefore, the average shadow area and polarizability are fundamental parameters that provide insight into the number of degrees of freedom for any object. These basic parameters also provide straightforward estimates of the minimum size of a device region required to support a desired number of electromagnetic degrees of freedom across a given spectral response.</p>}},
  author       = {{Gustafsson, Mats and Lundgren, Johan}},
  issn         = {{1045-9243}},
  language     = {{eng}},
  number       = {{6}},
  pages        = {{18--28}},
  publisher    = {{IEEE Computer Society}},
  series       = {{IEEE Antennas and Propagation Magazine}},
  title        = {{Degrees of Freedom and Characteristic Modes : Estimates for radiating and arbitrarily shaped objects}},
  url          = {{http://dx.doi.org/10.1109/MAP.2024.3389451}},
  doi          = {{10.1109/MAP.2024.3389451}},
  volume       = {{66}},
  year         = {{2024}},
}