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On the effect of a spherical shield on the radiation Q and efficiency of ideal dipole antennas

Sur l’influence d’une couche sphérique sur le facteur de qualité et le rendement des antennes dipôles idéales

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Abstract

A method is developed for calculating the radiation efficiency and quality factor, Q, for azimuthally symmetric electric (Tm) and magnetic (Te) multipole fields surrounded by a semi-transparent spherical shield of variable thickness, dielectric and magnetic constants involving losses. A matrix method is used to connect the transverse field components at adjacent interfaces. The Q and efficiency are determined by computing the energy stored in the near field of the multipole as well as the power radiated and dissipated in the shield. A numerical comparison of the performance of electric and magnetic dipole radiators is given as a function of frequency. An expression is derived for the permittivity of the shield which optimisés the Q.

Résumé

Nous présentons une méthode developpée pour calculer le rendement du rayonnement et le facteur de qualité, Q, d’un multipôle électrique (champTm) ou magnétique (champTe) omnidirectionel, enfermé dans un boîtier semi-transparent sphérique dont l’épaisseur, la per-mittivité et la perméabilité, y compris les pertes, sont variables. Une méthode matricielle est utilisée afin de lier les champs électromagnétiques transversaux sur des interfaces adjacentes. Le facteur Q et le rendement sont déterminés en calculant l’énergie stockée dans le champ proche du multipôle ainsi que la puissance rayonnée et absorbée dans le boîtier. La caractéristique d’un dipôle électrique est comparée numériquement à celle d’un dipôle magnétique en fonction de la fréquence. Une expression algébrique est trouvée pour la per-mittivité relative du boîtier qui optimiserait le facteur de qualité.

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Authors and Affiliations

  1. Technical Research Centre of Finland VTT, P. O. Box 1000, FI-02044, VTT, Finland

    Johan C. E. Sten & Arto Hujanen

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  1. Johan C. E. Sten
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  2. Arto Hujanen
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Sten, J.C.E., Hujanen, A. On the effect of a spherical shield on the radiation Q and efficiency of ideal dipole antennas. Ann. Télécommun. 61, 705–720 (2006). https://doi.org/10.1007/BF03219930

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  • DOI: https://doi.org/10.1007/BF03219930

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