| 1. |
- Cheney, Margaret, et al.
(författare)
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Optimal electromagnetic measurements
- 2001
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Ingår i: Journal Electromagnetic Waves and Applications. - 1569-3937. ; 15:10, s. 1323-1336
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Tidskriftsartikel (refereegranskat)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. |
- Cheney, Margaret, et al.
(författare)
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Optimal Electromagnetic Measurements
- 2000
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- We consider the problem of obtaining information about an inaccessible halfspace 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 wavesplitting 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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| 3. |
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| 4. |
- Derneryd, Anders, et al.
(författare)
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Antenna signal correlation and its relation to the impedance matrix
- 2004
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 40:7, s. 401-402
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Tidskriftsartikel (refereegranskat)abstract
- Theory is presented that extends the analysis to signal correlation between any antennas in an array of elements. It is generalised to include non-identical elements and arbitrary load termination of passive antenna ports. The method is related to the power balance concept and based on the antenna impedance matrix.
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| 5. |
- Derneryd, Anders, et al.
(författare)
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Mobile and terminal antennas
- 2003
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Ingår i: Antenn 03. Nordic Antenna Symposium. Conference Proceedings. ; , s. 37-38
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This project deals with the analysis of antennas for mobiles and terminals in the form of a patch element on a grounded substrate. A special case of this antenna element is the PIFA-element. The analysis is based on the propagator method, a vector generalisation of the transmission line theory, that has been extended to the analysis of surface waves in inhomogeneous permittivity profiles. Analyses of combined antenna radiation pattern and propagation channel characteristics have been initiated in order to demonstrate the performance advantage of exploiting two-antenna signals on a terminal for diversity or interference suppression. A generic two-antenna terminal is presented in this paper which improves capacity on reception. Signal correlation coefficients that depend on the mutual coupling are calculated.
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| 6. |
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| 7. |
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| 8. |
- Derneryd, Anders, et al.
(författare)
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Signal correlation including antenna coupling
- 2004
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Ingår i: Electronics Letters. - : Institution of Engineering and Technology (IET). - 1350-911X .- 0013-5194. ; 40:3, s. 157-159
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Tidskriftsartikel (refereegranskat)abstract
- Mutual coupling effects between antenna elements on signal correlation are reported. A simple expression is derived to compute the correlation coefficient from the far-field radiation patterns including the characteristics of the propagation environment and the terminating impedance. It is shown that the mutual coupling between closely spatially separated dipoles call lead to increased signal decorrelation.
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| 9. |
- Egorov, Igor, et al.
(författare)
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Transient electromagnetic wave propagation in laterally discontinuous, dispersive media
- 2001
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Ingår i: Wave Motion. - 0165-2125. ; 33:1, s. 67-77
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Tidskriftsartikel (refereegranskat)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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| 10. |
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