Circularly Polarized Receiving Antenna Incorporating Two Helices to Achieve Low Backscattering

We propose to use an antenna composed of two orthogonal helices as a low-scattering sensor. The vector effective length is derived for the antenna using the small dipole approximation for the helices. The antenna can transmit and receive circular polarization in all directions with the Huygens' pattern. We observe that the antenna geometry does not backscatter, regardless of the polarization, when the incidence direction is normal to the plane of the helices. Scattered fields, scattered axial ratio, and the scattering cross section are presented. We show that the zero-backscattering property holds also for the antenna when it is capable to receive all the available power with conjugate loading. The approximate analytical model is validated with full-wave simulations.Comment: 14 pages, 7 figures. Submitted to IEEE Trans. Antennas Propa

Isotropic Chiral Objects With Zero Backscattering

In this paper we study electrically small chiral objects with isotropic response and zero backscattering. A bi-isotropic sphere is used as a simple example and its zero-backscattering conditions are studied. A theoretical model of an object composed of three orthogonal chiral particles made of conducting wire is presented as an analog of the zero-backscattering bi-isotropic sphere. A potential application of the object as a receiving antenna or a sensor with the ability to receive power from an arbitrary direction without backscattering is discussed.Comment: 8 pages, 1 figure, submitted to IEEE Trans. Antennas Propa

Choosing Dielectric or Magnetic Material to Optimize the Bandwidth of Miniaturized Resonant Antennas

We address the question of the optimal choice of loading material for antenna miniaturization. A new approach to identify the optimal loading material, dielectric or magnetic, is presented for resonant antennas. Instead of equivalent resonance circuits or transmission-line models, we use the analysis of radiation to identify the fields contributing mostly to the stored energy. This helps to determine the beneficial material type. The formulated principle is qualitatively illustrated using three antenna types. Guidelines for different antenna types are presented.Comment: 17 pages, 9 figure

Finnish UNESCO school educators’ understanding of global citizenship education:analysis through typologies, ecosocial understanding, and human rights

Abstract This article sheds light on the unexplored field of UNESCO schools in Finland, and the results clarify the relationships between curricula, international commitments, and the understanding of educators in the educational field. It examines how teachers and principals of UNESCO’s Associated Schools Network (ASPnet) in Finland describe their understanding of the role of global citizenship education (GCE). It draws on the typology proposed by Oxley and Morris in which forms of global education are divided into cosmopolitan types and—more critically—advocacy types and subtypes. The article also draws on concepts connected to GCE in the Finnish curricula (namely, ecosocial understanding and human rights). Findings indicate that educators perceived equality, democracy, and ecological sustainability as part of UNESCO schools and their own work. On the other hand, the need for increasing student-centered approaches was noted, racism was perceived as a difficult topic, and active deconstruction of inequalities was less referenced. When analyzing the results through typologies of global citizenship, the critical, spiritual, and economic aspects of GCE received less attention

Electromagnetic interaction with uniaxial metamaterials

In this paper, the reflection behavior of a particular class of metamaterials, strongly connected with the realization of the DB boundary conditions (so called due to the vanishing of the normal components of the D and B fluxes) and the soft and hard (SH) boundary conditions, is presented. The metamaterial under study is modeled as an anisotropic, uniaxial, material with both permittivity and permeability dyadics. We consider several characteristics of such medium: presenting the critical angle of total transmission for the SH/DB material, analyzing its behavior as a function of the longitudinal permittivity and permeability, for both positive and negative values, and presenting its applications to the electromagnetic absorbers and to the polarization inverters.Peer reviewe