| 1. |
- Cheney, Margaret, et al.
(author)
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Optimal electromagnetic measurements
- 2001
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In: Journal Electromagnetic Waves and Applications. - 1569-3937. ; 15:10, s. 1323-1336
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Journal article (peer-reviewed)abstract
- We consider the problem of obtaining information about an inaccessible half-space from electromagnetic measurements made in the accessible half-space. If the measurements are of limited precision, some scatterers will be undetectable because their scattered fields are below the precision of the measuring instrument. How can we make optimal measurements? In other words, what incident fields should we apply that will result in the biggest measurements? There are many ways to formulate this question, depending on the measuring instruments. In this paper we consider a formulation involving wave-splitting in the accessible half-space: what downgoing wave will result in an upgoing wave of greatest energy? This formulation is most natural for far-field problems. A closely related question arises in the case when we have a guess about the configuration of the inaccessible half-space. What measurements should we make to determine whether our guess is accurate? In this case we compare the scattered field to the field computed from the guessed configuration. Again we look for the incident field that results in the greatest energy difference. We show that the optimal incident field can be found by an iterative process involving time reversal "mirrors". For band-limited incident fields and compactly supported scatterers, this iterative process converges to a sum of time-harmonic fields.
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| 2. |
- Egorov, Igor, et al.
(author)
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Transient electromagnetic wave propagation in laterally discontinuous, dispersive media
- 2001
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In: Wave Motion. - 0165-2125. ; 33:1, s. 67-77
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Journal article (peer-reviewed)abstract
- This paper concerns propagation of transient electromagnetic waves in laterally discontinuous dispersive media. The approach, used here, employs a component decomposition of all fields. Specifically, the propagation operator that maps a transverse field on one plane to another plane is specified. Expansion of this mapping near the wave front determines the precursor or forerunner of the problem.
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| 6. |
- Kristensson, Gerhard, et al.
(author)
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Propagators and scattering of electromagnetic waves in planar bianisotropic slabs - an application to frequency selective structures
- 2001
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Reports (other academic/artistic)abstract
- Scattering by planar geometries with plane metal inclusions are analyzed. The metal inclusions can be of arbitrary shape, and the material of the supporting slabs can be any linear (bianisotropic) material. We employ the method of propagators to find the solution of the scattering problem. The method has certain similarities with a vector generalization of the transmission line theory. A general relation between the electric fields and the surface current densities on the metal inclusions and the exciting fields are found. Special attention is paid to the case of a periodic metal pattern (frequency selective structures, FSS). The method is illustrated by a series of numerical computations.
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| 8. |
- Kristensson, Gerhard, et al.
(author)
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Radiation efficiency and surface waves for patch antennas on inhomogeneous substrat
- 2001
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Reports (other academic/artistic)abstract
- In this paper the surface wave characteristics, as well as the radiation efficiency and the directivity of a patch antenna, with a given current distribution, located on top of an inhomogeneous, isotropic substrate are calculated. The substrate is infinite in the lateral directions and inhomogeneous with respect to the height coordinate. The surface waves in the substrate are analyzed using the propagator technique and residue calculus. The propagators and the residues are found by solving two sets of systems of ordinary differential equations (ODEs). Several dispersion curves of the surface waves for inhomogeneous substrates are calculated. The radiation efficiency and the directivity are compared with the corresponding quantities of a printed antenna on a homogenized substrate. Moreover, some alternative ways of calculating the reflection dyadic of an inhomogeneous substrate are presented in a series of appendices.
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| 10. |
- Rikte, Sten, et al.
(author)
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Propagation in bianisotropic media-reflection and transmission
- 2001
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In: IEE Proceedings - Microwaves Antennas and Propagation. - : Institution of Engineering and Technology (IET). - 1350-2417. ; 148:1, s. 29-36
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Journal article (peer-reviewed)abstract
- A systematic analysis for solving the wave propagation problem in a general bianisotropic, stratified medium is presented. The method utilises the concept of propagators, and the representation of these operators is simplified by introducing the Cayley-Hamilton theorem. The propagators propagate the total tangential electric and magnetic fields in the slab and only outside the slab do the up- and down-going parts of the fields need to be identified. This procedure makes the physical interpretation of the theory intuitive. The reflection and the transmission dyadics for a general bianisotropic medium with an isotropic (vacuum) half-space on both sides of the slab are presented in a co-ordinate-independent dyadic notation, as well as the reflection dyadic for a bianisotropic slab with perfectly electric backing (PEC). In the latter case the current on the metal backing is also given. Some numerical computations that illustrate the algorithm are presented
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