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Sökning: LAR1:lu > Sjöberg Daniel > Rapport

  • Resultat 1-10 av 33
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1.
  • Andersson, Michael, et al. (författare)
  • Stabilization of evanescent wave propagation operators
  • 2022
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • This paper presents a stabilized scheme that solves the wave propagation problem in a general bianisotropic, stratified medium. The method utilizes the concept of propagators, i.e., the wave propagation operators that map the total tangential electric and magnetic fields from one plane in the slab to another. The scheme transforms the propagator approach into a scattering matrix form, where a spectral decomposition of the propagator enables separation of the exponentially growing and decaying terms in order to obtain a well-conditioned formulation. Multilayer structures can be handled in a stable manner using the dissipative property of the Redheffer star product for cascading scattering matrices. The reflection and transmission dyadics for a general bianisotropic medium with an isotropic half space on both sides of the slab are presented in a coordinate-independent dyadic notation, as well as the reflection dyadic for a bianisotropic slab with perfect electric conductor backing (PEC). Several numerical examples that illustrate the performance of the stabilized algorithm are presented.
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2.
  • Bondarik, Alexander, et al. (författare)
  • Gridded Parasitic Patch Stacked Microstrip Antenna With Beam Shift Capability for 60 GHz Band
  • 2014
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • A microstrip antenna design is introduced in which a rectangular microstrip patch is coupled electromagnetically with a gridded rectangular patch placed above. The gridded patch consists of nine identical rectangular parts separated by a distance which is much smaller than a free space wavelength for a central frequency. The antenna is designed to operate in the 60 GHz band and is fabricated on a conventional PTFE (polytetrafluoroethylene) thin substrate. The antenna return loss bandwidth is comparable to a single parasitic patch aperture coupled antenna, while the proposed antenna gain is higher. Measurement results are in good agreement with simulation. Measured 10 dB return loss bandwidth is from 54 GHz up to 67 GHz. It fully covers the unlicensed band around 60 GHz. The measured antenna realized gain at 60 GHz is close to 8 dB, while the simulated antenna radiation efficiency is 85%. A simple beam shifting method is possible for this antenna structure by connecting adjacent outside parts in the gridded patch. The designed antenna is suitable for a high speed wireless communication system in particular for a user terminal in a fifth generation (5G) cellular network.
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  • Gustafsson, Mats, et al. (författare)
  • Optical theorem and forward scattering sum rule for periodic structures
  • 2011
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • Based on energy conservation, an optical theorem is constructed for a slab having an arbitrary periodic microstructure in a plane. A sum rule for low pass structures is derived using analytic properties of Herglotz functions based on causality and passivity. The sum rule relates the extinction cross section to the static polarizability per unit cell, and quantifies the interaction between the slab and electromagnetic fields possible over all wavelengths. The results are illustrated with several numerical and experimental examples.
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  • Gustafsson, Mats, et al. (författare)
  • Physical bounds and sum rules for high-impedance surfaces
  • 2010
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • High-impedance surfaces are artificial surfaces synthesized from periodic structures. The high impedance is useful as it does not short circuit electric currents and reflects electric fields without phase shift. Here, a sum rule is presented that relates frequency intervals having high impedance with the thickness of the structure. The sum rule is used to derive physical bounds on the bandwidth for high-impedance surfaces. Numerical examples are used to illustrate the result, and show that the physical bounds are tight.
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10.
  • Karlsson, Anders, et al. (författare)
  • Frequency Selective Structures with Stochastic Deviations
  • 2003
  • Rapport (övrigt vetenskapligt/konstnärligt)abstract
    • This paper deals with the performance of frequency selective structures with defects. A frequency selective structure is in this case a periodic pattern of apertures in a conducting plate. The plate can be of arbitrary thickness. The defects can be by deviations in the placing of the apertures, in the material parameters, or in the shape of the apertures. First the perturbation to the far- field pattern from a deviation in one aperture is analyzed. Then a statistical analysis is performed for a frequency selective structure where the apertures have a stochastic variation.
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  • Resultat 1-10 av 33

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