| 21. |
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| 22. |
- Engström, Christian, et al.
(författare)
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Numerical methods for homogenization of Maxwell's equations
- 2004
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Ingår i: URSI 2004 International Symposium on Electromagnetic Theory. - : Pisa University Press. - 8884922526 - 9788884922526 ; , s. 987-989
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Konferensbidrag (refereegranskat)abstract
- When the wavelength is much larger than the typical scale of the microstructure in a material, it is possible to define effective or homogenized material coefficients. Two numerical methods for the determination of the homogenized coefficients are compared. Numerical examples, where extreme properties of the effective material are achieved in the two dimensional case, are presented.
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| 23. |
- Engström, Christian, et al.
(författare)
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On two numerical methods for homogenization of Maxwell's equations
- 2007
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Ingår i: Journal Electromagnetic Waves and Applications. - : Taylor & Francis. - 0920-5071 .- 1569-3937. ; 21:13, s. 1845-1856
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Tidskriftsartikel (refereegranskat)abstract
- When the wavelength is much larger than the typical scale of the microstructure in a material, it is possible to define effective or homogenized material coefficients. The classical way of determination of the homogenized coefficients consists of solving an elliptic problem in a unit cell. This method and the Floquet-Bloch method, where an eigenvalue problem is solved, are numerically compared with respect to accuracy and contrast sensitivity. Moreover, we provide numerical bounds on the effective permittivity. The Floquet-Bloch method is shown to be a good alternative to the classical homogenization method, when the contrast is modest.
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| 24. |
- Ericsson, Andreas, et al.
(författare)
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A combined electromagnetic and acoustic analysis of a triaxial carbon fiber weave for reflector antenna applications
- 2016
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Ingår i: Aerospace Science and Technology. - : Elsevier. - 1270-9638 .- 1626-3219. ; 58, s. 401-417
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Tidskriftsartikel (refereegranskat)abstract
- Fiber composites are widely used for space applications such as antennas, solar panels and spacecraft support structures. This paper presents a combined electromagnetic and acoustic analysis of a triaxial carbon fiber weave structure, designed for ultra lightweight reflector antennas in satellite communication systems. The electromagnetic and acoustic performance of the structure are analyzed over a wide range of parametric studies, both at a microscopic and mesoscopic length scale. The electromagnetic study indicates that the main parameter governing the electromagnetic reflection performance of the weave is the electric conductivity of the carbon fibers, given that the weave structure is significantly smaller than the wavelength of the incident signals. The acoustic study identifies a critical threshold in the mesoscale geometry in order to avoid a critically high resistive behavior of the weave structure, driven by viscous effects. Design guidelines are drawn from these analyses in order to achieve a trade-off between the electromagnetic reflection properties and the resistance to acoustic loading of such composite materials. These combined analyses allow to deepen the understanding from both an electromagnetic and acoustic perspective in order to open for some new design possibilities.
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| 25. |
- Ericsson, Andreas, et al.
(författare)
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A Performance Study of Circular Polarization Selective Structures
- 2015
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Ingår i: [Host publication title missing].
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Konferensbidrag (refereegranskat)abstract
- A circular polarization selective structure (CPSS) reflects one handedness of circular polarization and transmits the other. In this paper the performance of a number of classical CPSS designs has been evaluated at the center frequency of operation for all possible spherical incidence angles. The results are presented in a compact way using two dimensional contour plots to represent the return loss, insertion loss and polarization purity of the transmitted and reflected signals. The results indicate that all CPSS designs presented up to date have preferred incidence planes of operation. The existence of geometrical symmetries in the designs affect the performance stability of the structures with respect to oblique angles of incidence. Applications of CPSSs in satellite communication systems, for example as a circular polarization dual aperture antenna or a circular polarization diplexer, require the structures to operate at wide ranges of oblique angles of incidence, making this type of analysis crucial for future development and evaluation of circular polarization selective structures.
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| 26. |
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| 27. |
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| 28. |
- Ericsson, Andreas, et al.
(författare)
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Approximative computation methods for monostatic scattering from axially symmetric objects
- 2017
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Ingår i: Progress In Electromagnetics Research B. - 1937-6472. ; 79, s. 127-147
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Tidskriftsartikel (refereegranskat)abstract
- Two approximation methods are presented for fast calculations of the monostatic scattering from axially symmetric scatterers coated with electromagnetic absorbers. The methods are designed for plane wave illumination parallel to the axis of rotation of the scatterer. The first method is based on simulating the scattering of a perfect electric conductor (PEC) enclosing the absorber coated scatterer, and multiplying the result with the squared magnitude of the absorber reflection coefficient in a planar scenario. The second method is based on simulating the scattering scenario in a physical optics (PO) solver, where the electromagnetic absorber is treated as reflection dyadic at the outer surface of the scatterer. Both methods result in a significant acceleration in computation speed in comparison to full wave methods, where the PO method carries out the computations in a number of seconds. The monostatic scattering from different geometries have been investigated, and parametric sweeps were carried out to test the limits where the methods yield accurate results. For specular reflections, the approximation methods yield very accurate results compared to full wave simulations when the radius of curvature is on the order of half a wavelength or larger of the incident signal. It is also concluded that the accuracy of the two methods varies depending on what type of absorber is applied to the scatterer, and that absorbers based on "volume losses" such as a carbon doped foam absorber and a thin magnetic absorber yield better results than absorbers based on resistive sheets, such as a Salisbury absorber.
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| 29. |
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