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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 composed by periodic structures above a perfectly conducting ground plane. Numerical examples are used to illustrate the result, and show that the physical bounds are tight.
IEEE Transactions on Antennas and Propagation 07/2011; · 2.15 Impact Factor
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ABSTRACT: The objective of this paper is to review some recently developed sum rules and physical bounds in scattering and antenna theory. The sum rules are based on identities for Herglotz functions that relate the quantity of interest integrated over all wavelengths with its static polarizability dyadics. They are transformed to physical bounds by applying variational principles for the polarizability dyadics together with various estimates of the integrals. The theoretical findings are exemplified by numerical results for several configurations.
Electromagnetics in Advanced Applications, 2009. ICEAA '09. International Conference on; 10/2009
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ABSTRACT: The elementary split ring resonator is a key structure in so-called ldquometamaterialrdquo mediums. In this presentation, low-frequency electromagnetic scattering by a split ring, modelled as a perfectly conducting wire ring furnished with a narrow gap, is presented and analytical results are given for the electric and magnetic dipole moments for different kinds of incidence and polarisation in the quasi-static approximation. Through the process of homogenisation, the expressions discovered for the dipole moments and the related polarisation dyadics are linked with the macroscopic constitutive equations for the medium.
Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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ABSTRACT: We report on the design and the first steps in the manufacturing of a dielectric resonator antenna, codesigned with an oscillator circuit for impulse radio at 60 GHz. The realization of the impulse radio function is of very low complexity, and is based on a gated tunnel diode on a GaAs substrate. In particular, we have studied the design of the antenna structure and its matching with the electrical properties of the oscillator circuit where the antenna is integrated.
Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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ABSTRACT: The objective of this paper is to give an overview of some recently developed sum rules and physical bounds in scattering and antenna theory. The sum rules are based on integral identities for Herglotz functions that relate the quantity of interest with its low and high-frequency behavior. The sum rules are transformed to bounds by estimating the integrals and applying variational results to the parameters that appear in the asymptotic expansions. The theoretical findings are exemplified by numerical results for various scattering and antenna configurations.
Antennas and Propagation, 2009. EuCAP 2009. 3rd European Conference on; 04/2009
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D. Sjoberg
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ABSTRACT: The construction of thin, broad band absorbers using magnetic materials rely on the presence of high magnetic losses. In this paper, we discuss the possibilities of realizing these losses by studying the Landau-Lifshitz-Gilbert model of ferromagnetic materials. The small signal permeability derived from this nonlinear model is then combined with modern homogenization techniques to study a composite material made up of nanosized magnetic particles embedded in a background material. This is used to produce bounds in the complex plane as to what effective material parameters can be achieved from such a composite material.
Antennas and Propagation, 2007. EuCAP 2007. The Second European Conference on; 12/2007
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ABSTRACT: The topic of this paper is the work carried out in Work Package 2.3-2 of the EU network ACE. This work package is concerned with the modelling of the surfaces of modern reflector antennas. In particular the problems associated with homogenisation are described together with an application example. Fast, but approximate, methods are compared to rigorous solutions for realistic strip grid configurations. A new, fast and very efficient interpolation technique for frequency selective surfaces is introduced.
Antennas and Propagation, 2006. EuCAP 2006. First European Conference on; 12/2006
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ABSTRACT: We compare two method of moments codes using RWG elements for two- dimensional periodicity. The test cases are common elements employed in the design of frequency selective surfaces: crossed dipoles, tripoles, and linear dipoles. The last case is also examined with a supporting dielectric substrate. It is shown that the codes agree very well. One of the codes does not imple- ment a layered Green's function, and is therefore much slower when studying the dielectric substrate since a lot of degrees of freedom are spent on discretiz- ing this structure. There is also a larger difference between the codes in this case.
