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Item type:Publication, Access status: with files , A statistical study of scattering in periodic and random helix layersThis paper aims at providing information on scattering in layers composed of periodic and non-periodic arrangements of small metal helices. Metal helices exhibit a pronounced resonance and are thus very effective scatterers.Publicationtype: Journal Article320 551 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multipole scattering in periodic and random layers of metal helices(2009-06); Scattering in layers composed of periodic and non-periodic arrangements of small metal helices is discussed. Metal helices exhibit a pronounced resonance and are thus very effective scatterers. Scattering is expressed in terms of multipole moments. The investigations show that only few multipole contributions are necessary to model the interaction correctly.Publicationtype: Conference Paper43 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Multipolinteraktionen in geordneten und ungeordneten Schichten kleiner metallischer HelicesPublicationtype: Doctoral Thesis26 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Higher order multipole model of a thin-wire helixWe investigate the field scattered from thin-wire helices by means of vector spherical harmonics rendering the fields of generated multipoles of arbitrary order. The excitation is varied in order to yield the characteristic T-matrix of a single helix column by column. The convergence with respect to the number and kind of required multipoles is checked by means of a simple test case. Further, we consider the mutual interaction of two helices. It is shown to be equivalent to an averaging process in terms of the number of required multipoles, which is thus limited. The helix model is then utilized to investigate reflection and transmission properties of a specific periodic arrangement which allows a comparison to a finite element based commercial software tool.Publicationtype: Journal Article38 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical and experimental parameter study of helix layersThe focus of this contribution is on the scattering of small metal helices in layered arrangements that are located in free space or backed with a perfect electric conductor. Thereby, the S-parameters obtained by means of a scattering approach based on the dipole-polarizabilities of the helices serve as a reference for the studies. The method accounts for the discrete particle positions. However, for practical reasons some averaging is involved. An analysis of fabricated inclusions appears to be essential for a comparison of the utilized method with measurements of material samples. Good agreement is confirmed by varying the thickness of the layer as well as the density of the inclusions. Further, the applicability of the Clausius-Mossotti mixing rule to the presented setups is critically assessed by comparison. In principle, it turns out that the scattering derived via classical effective material parameters differs from the one of the actual layers. Nevertheless, mixing rules could still be a method of choice if mutual coupling were not as strong as in the cases considered here.Publicationtype: Journal Article67 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , T-Matrix methods for collections of thin-wire scatterers(2008-04); Publicationtype: Conference Paper25 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analysis, fabrication, and measurement of frequency-selective helix layersPublicationtype: Journal Article46 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Analysis and fabrication of a frequency-selective helix layerWe investigate a layer composed of periodically placed copper helices. Thereby, left- and right-turned helices form a chessboard-like pattern. In this manner, cross-polarized field components which are inherent to helical particles cancel out. According to theory, this setup features nearly full reflection at resonance. The single-scatterer resonance of a representative number of particles is examined experimentally in order to assess manufacturing tolerances. The latter are taken into account by a numerical scattering approach being able to determine reflection and transmission characteristics. For experimental verification, the scatterers are mounted in commercially available plastic foam. To reduce the effect of manufacturing tolerances, smallstructured profiles are cut out by means of a laser beam. A fabricated sample consisting of a total of 3600 helices is characterized by means of a free-space measurement setup.Publicationtype: Conference Paper47 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical aspects in the analysis of infinite regular and random helix arraysThis contribution focuses on a scattering description of infinite arrays of small metallic helices. The latter are assumed to scatter like dipoles. A numerical approach is extended to account for the influence of the lattice with more precision. This is done by a simple extrapolation scheme, which accelerates the convergence of the arising series. For regular arrays, a comparison with a commercial software tool reveals a good agreement, at least as long as the distance between the particles is large enough for the dipole assumption to be valid. This also applies at resonance, the most critical case. The effects on random arrays are also investigated. © 2007 Wiley Periodicals, Inc.Publicationtype: Journal Article48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Fast numerical analysis of infinite helix layersThe scattering of particles is described by multipole moments up to the electric quadrupole contribution. A method for the calculation of reflection and transmission from thin composite layers is derived. The approach uses periodic boundary conditions. The validity of the approach is checked by considering thin chiral layers composed of small metal helices. The investigations are performed in the frequency domain and include the resonance case.Publicationtype: Journal Article39