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Sökning: LAR1:lu > Gustafsson Mats > Fritt online > Sohl Christian > Linnéuniversitetet

  • Resultat 1-5 av 5
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  • Gustafsson, Mats, et al. (författare)
  • An overview of some recent physical bounds in scattering and antenna theory
  • 2009
  • Konferensbidrag (refereegranskat)abstract
    • The objective of this paper is to give an overview of some recently developed sum rules and physical bounds in scattering and antenna theory. The sum rules are based on integral identities for Herglotz functions that relate the quantity of interest with its low and high-frequency behavior. The sum rules are transformed to bounds by estimating the integrals and applying variational results to the parameters that appear in the asymptotic expansions. The theoretical findings are exemplified by numerical results for various scattering and antenna configurations.
  • Gustafsson, Mats, et al. (författare)
  • Physical bounds on the antenna scattering matrix
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • The antenna scattering matrix is based on a spherical vector wave expansion and contains a complete description of the matching, transmission, receiving, and scattering properties of an antenna. It is commonly utilized in near-field measurements and it can also be used to model MIMO antennas. Here, an approach based on the holomorphic properties of the antenna scattering matrix is used to derive physical bounds on the bandwidth of lossless antennas. The resulting bounds are expressed in the radius of the smallest circumscribing sphere and the polarizability dyadics of the antenna. The derivation and final results resemble both the classical work by Chu (1948) and a recently developed theory based on the forward scattering. However, instead of estimating the Q-factor through the stored energy, the low-frequency expansion of the scattering matrix is used to obtain a set of summation rules from which bounds on the bandwidth are derived. The use of Cauchy integrals and the low-frequency expansion in terms of the polarizability dyadics are similar with the approach in (Chu, 1948 and Gustafsson et al., 2007).
  • Nordebo, Sven, et al. (författare)
  • On the relation between optimal wideband matching and scattering of spherical waves
  • 2011
  • Ingår i: IEEE Transactions on Antennas and Propagation1963-01-01+01:00. - IEEE--Institute of Electrical and Electronics Engineers Inc.. - 0018-926X. ; 59:9, s. 3358-3369
  • Tidskriftsartikel (refereegranskat)abstract
    • Abstract in Undetermined Using an exact circuit analogy for the scattering of vector spherical waves, it is shown how the problem of determining the optimal scattering bounds for a homogeneous sphere in its high-contrast limit is identical to the closely related, and yet very different problem of finding the broadband tuning limits of the spherical waves. Using integral relations similar to Fano’s broadband matching bounds, the optimal scattering limitations are determined by the static response as well as the high-frequency asymptotics of the reflection coefficient. The scattering view of the matching problem yields explicitly the necessary low-frequency asymptotics of the reflection coefficient that is used with Fano’s broadband matching bounds for spherical waves, something that appears to be non-trivial to derive from the classical network point of view.
  • Sohl, Christian, et al. (författare)
  • A general approach for deriving bounds in electromagnetic theory
  • 2008
  • Konferensbidrag (refereegranskat)abstract
    • This paper reports on a systematic procedure for deriving physical bounds in electromagnetic theory. The approach is based on the holomorphic properties of certain Herglotz functions and their asymptotic expansions in the low- and high-frequency regimes. A family of integral identities or summation rules is obtained with values governed by the coefficients in the low- and high-frequency expansions. In particular, summation rules for plane-wave scattering by a homogenous and isotropic sphere is derived and verified numerically by computing the extinction cross section and the bistatic radar cross section in the forward direction. It is concluded that summation rules based on Herglotz functions show great potential for deriving new physical bounds in, e.g., scattering and antenna problems.
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  • Resultat 1-5 av 5
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konferensbidrag (4)
tidskriftsartikel (1)
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refereegranskat (5)
Nordebo, Sven, (5)
Kristensson, Gerhard ... (4)
Bernland, Anders, (2)
Larsson, Christer, (1)
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Sjöberg, Daniel, (1)
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Lunds universitet (5)
Engelska (5)
Forskningsämne (UKÄ/SCB)
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