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Showing papers by "Per-Simon Kildal published in 1996"


Journal ArticleDOI
TL;DR: In this article, the authors derived a relation between the blockage width and the bistatic scattering width, and showed how cylinders such as struts and masts can be constructed to reduce their blockages.
Abstract: We discuss how forward scattering can he characterized in terms of an equivalent blockage width, and a relation between this and the bistatic scattering width is derived. Then, we show how cylinders such as struts and masts can be constructed to reduce their blockage widths. Thereby, when the cylinders are mounted in front of an antenna, the sidelobes and losses caused by the blockage will be reduced. For thin metal cylinders the blockage width reduction is obtained by giving its cross section an oblong shape and, in addition (for the TM case), by coating the outer metal surface with dielectric material to obtain a hard boundary condition. For thick cylinders, the reduced scattering is obtained by designing them as dielectric-filled parallel plate waveguides with the outer surfaces of the plates coated in the same way as for the thin struts. Dual-polarized performance is obtained in both cases by strip loading the outer surfaces. The performance of both the thin and the thick struts have limited frequency bandwidth. Both computed and measured results are presented; the computations being done with the moment method. The designs are based on the concept of soft and hard surfaces in electromagnetics, and the results can be regarded as a proof of the existence of hard surfaces for electromagnetic waves. The study considers reduction of forward scattering which also will give a reduction of the total integrated power of the scattered field over all directions-even backward.

198 citations


01 Jan 1996
TL;DR: In this article, the unidirectional current screen was used as an asymptotic strip boundary condition (ASBC) for analysis of field problems containing metal strip grids.
Abstract: We discuss the unidirectional current screen as an asymptotic strip boundary condition (ASBC) for analysis of field problems containing metal strip grids, and we introduce a related asymptotic corrugation boundary condition (ACBC) for analysis of corrugated surfaces. The boundary conditions are asymptotic in the sense that the exact boundary conditions approach the asymptotic ones when the strip and corrugation periods approach zero. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 14: 99–101, 1997.

69 citations


Journal ArticleDOI
01 Jun 1996
TL;DR: In this paper, a study of some elementary antennas, such as a dipole, a waveguide aperture, a microstrip patch, a spiral and a helix, when they are mounted on a ground plane with circular corrugations acting as a soft surface is presented.
Abstract: The paper presents a study of some elementary antennas, such as a dipole, a waveguide aperture, a microstrip patch, a spiral and a helix, when they are mounted on a ground plane with circular corrugations acting as a soft surface. The results of both experiments and calculations are described. The latter have been done either by the uniform geometrical theory of diffraction (UTD) or by the moment method (MM), and are in good agreement with the measurements. It is found that the corrugated soft ground plane makes the radiation patterns of all the antennas more rotationally symmetric with lower sidelobe levels and lower crosspolarisation when compared to using a smooth conducting ground plane.

51 citations


Journal ArticleDOI
TL;DR: In this article, the Finite Difference Time Domain (FDTD) method is applied to industrial microwave ovens used in the food industry and theoretical and practical aspects of FDTD analysis for this purpose are dealt with.
Abstract: The Finite Difference Time Domain (FDTD) method is applied to industrial microwave ovens used in the food industry. Theoretical and practical aspects of FDTD analysis for this purpose are dealt wit...

31 citations





Proceedings ArticleDOI
01 Oct 1996
TL;DR: In this paper, a rotationally symmetric cellular phone with a monopole antenna is comprehensively analyzed and the radiation efficiency is studied as a function of the size of the phone body and of the antenna length.
Abstract: A rotationally symmetric cellular phone with a monopole antenna is comprehensively analysed. The radiation efficiency is studied as a function of the size of the phone body and of the antenna length. Further, the possibility of shortening the monopole by coating it with a highpermittivity dielectric at the monopole is investigated. All calculations are performed both with and without a model of a human hand holding the phone. The Method of Moments is used for the simulations and the results are confirmed by measurements. A very good agreement is observed.

1 citations