| 31. |
- Nordebo, Sven, et al.
(författare)
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On the relation between optimal wideband matching and scattering of spherical waves
- 2011
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 59:9, s. 3358-3369
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Tidskriftsartikel (refereegranskat)abstract
- Abstract in UndeterminedUsing an exact circuit analogy for the scattering ofvector spherical waves, it is shown how the problem of determiningthe optimal scattering bounds for a homogeneous spherein its high-contrast limit is identical to the closely related, andyet very different problem of finding the broadband tuning limitsof the spherical waves. Using integral relations similar to Fano’sbroadband matching bounds, the optimal scattering limitationsare determined by the static response as well as the high-frequencyasymptotics of the reflection coefficient. The scattering view of thematching problem yields explicitly the necessary low-frequencyasymptotics of the reflection coefficient that is used with Fano’sbroadband matching bounds for spherical waves, something thatappears to be non-trivial to derive from the classical networkpoint of view.
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| 32. |
- Nordebo, Sven, et al.
(författare)
-
Optimal Realizations of Passive Structures
- 2014
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Ingår i: IEEE Transactions on Antennas and Propagation. - 0018-926X .- 1558-2221. ; 62:9, s. 4686-4694
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a convex optimization approach to study optimal realizations of passive electromagnetic structures. The optimization approach complements recently developed theory and techniques to derive sum rules and physical limitations for passive systems operating over a given bandwidth. The sum rules are based solely on the analytical properties of the corresponding Herglotz functions. However, the application of sum rules is limited by certain assumptions regarding the low- and high-frequency asymptotic behavior of the system, and the sum rules typically do not give much information towards an optimal realization of the passive system at hand. In contrast, the corresponding convex optimization problem is formulated to explicitly generate a Herglotz function as an optimal realization of the passive structure. The procedure does not require any additional assumptions on the low- and high frequency asymptotic behavior, but additional convex constraints can straightforwardly be incorporated in the formulation. Typical application areas are concerned with antennas, periodic structures, material responses, scattering, absorption, reflection, and extinction. In this paper, we consider three concrete examples regarding dispersion compensation for waveguides, passive metamaterials and passive radar absorbers.
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| 33. |
- Nordebo, Sven, et al.
(författare)
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Statistical Signal Analysis for the Inverse Source Problem of Electromagnetics
- 2006
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Ingår i: IEEE Transactions on Signal Processing. - 1053-587X. ; 54:6, s. 2357-2361
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Tidskriftsartikel (refereegranskat)abstract
- A statistical signal analysis for the inverse source problem of electromagnetics is given. We consider the problem of estimating either the near field or the radiating current distribution from a measurement of the far field. The solution is derived via a linear operator formalism, and the ill-posedness of the reconstruction is quantified by using the Cramer-Rao lower bound which is explicitly given in terms of the multipole expansion of the electromagnetic field. A numerical study is included to illustrate the theoretical results.
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| 34. |
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| 35. |
- Nordebo, Sven, et al.
(författare)
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Wave modeling and fault localization for underwater power cables
- 2011
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Ingår i: 2011 IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC). - : IEEE Press. - 9781457700460 ; , s. 698-701
-
Konferensbidrag (refereegranskat)abstract
- This paper describes some preliminary results regarding Time-Domain pulse Reflection (TDR) measurements and modeling performed on the Baltic Cable submarine HVDC link between southern Sweden and northern Germany. The measurements were conducted in collaboration between the Linnaeus University, Lund University, Baltic Cable AB and ABB High Voltage Cables AB, and is part of the research project: “Fundamental wave modeling for signal estimation on lossy transmission lines”. Preliminary results on measurements and modeling are included here, as well as a first numerical study regarding the low-frequency dispersion characteristics of power cables. The numerical study shows that the finite conductivity of the cable lead shield has a great impact on the losses at low frequencies (0-1 kHz), and that the low-frequency asymptotics of the propagation constant is consistent with common propagation models based on the skin-effect.
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| 36. |
- Proto, Monica, et al.
(författare)
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Transport Infrastructure Surveillance and Monitoring by Electromagnetic Sensing : The ISTIMES Project
- 2010
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Ingår i: Sensors. - : MDPI AG. - 1424-8220. ; 10:12, s. 10620-10639
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Tidskriftsartikel (refereegranskat)abstract
- The ISTIMES project, funded by the European Commission in the frame of a joint Call "ICT and Security" of the Seventh Framework Programme, is presented and preliminary research results are discussed. The main objective of the ISTIMES project is to design, assess and promote an Information and Communication Technologies (ICT)-based system, exploiting distributed and local sensors, for non-destructive electromagnetic monitoring of critical transport infrastructures. The integration of electromagnetic technologies with new ICT information and telecommunications systems enables remotely controlled monitoring and surveillance and real time data imaging of the critical transport infrastructures. The project exploits different non-invasive imaging technologies based on electromagnetic sensing (optic fiber sensors, Synthetic Aperture Radar satellite platform based, hyperspectral spectroscopy, Infrared thermography, Ground Penetrating Radar-, low-frequency geophysical techniques, Ground based systems for displacement monitoring). In this paper, we show the preliminary results arising from the GPR and infrared thermographic measurements carried out on the Musmeci bridge in Potenza, located in a highly seismic area of the Apennine chain (Southern Italy) and representing one of the test beds of the project.
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| 37. |
- Sjöberg, Daniel, et al.
(författare)
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Convex optimization for optimal realization of material properties
- 2014
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Ingår i: 2014 International Conference on Electromagnetics in Advanced Applications (ICEAA), 3-8 Aug. 2014, Palm Beach. - : IEEE Press. - 9781479973255 ; , s. 782-785
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Konferensbidrag (refereegranskat)abstract
- We show how the best passive approximation to a given target material or structure can be found byconvex optimization. The approach is based on a representation of positive real functions, where some of the parameters can be given physical relevance by comparison to low- and high-frequency asymptotics of the material or structure under study. A number of different optimization problems can be formulated, which generalizes previous approaches using sum rules.
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| 38. |
- Vakili, Iman, et al.
(författare)
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Sum Rules for Parallel-Plate Waveguides : Experimental Results and Theory
- 2014
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Ingår i: IEEE transactions on microwave theory and techniques. - 0018-9480 .- 1557-9670. ; 62:11, s. 2574-2582
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Tidskriftsartikel (refereegranskat)abstract
- An experimental approach to investigate the forward scattering sum rule for periodic structures is presented. This approach allows an upper bound on the total cross section integrated over a bandwidth from a simple static problem to be found. Based on energy conservation, the optical theorem is used to construct a relation between the total cross section and the forward scattering of periodic structures as well as single scatterers inside a parallel-plate waveguide. Dynamic measurements are performed using a parallel-plate waveguide and a parallel-plate capacitor is utilized to find the static polarizability. Convex optimization is introduced to identify the total cross section in the dynamic measurements and estimate an optimal lower bound on the polarizability for objects. The results show that the interactions between the electromagnetic field and an object over all wavelengths are given by the static polarizability of the object.
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