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Comptes Rendus Physique
Volume 16, n° 9
pages 789-801 (novembre 2015)
Doi : 10.1016/j.crhy.2015.10.005
Body area networks at radio frequencies: Creeping waves and antenna analysis
Réseaux de communication corporels aux fréquences radio : ondes rampantes et analyse des antennes
 

Khaleda Ali a , Farshad Keshmiri b , Alessio Brizzi a , Yang Hao a , Christophe Craeye c,
a Queen Mary University London, Electrical Eng. Dept., Mile End Road, E1 4NS London, UK 
b ART-FI, 27, rue Jean-Rostand, Parc Club Orsay Université, 91400 Orsay, France 
c Université catholique de Louvain, place du Levant, 3, ICTEAM Institute, Louvain-la-Neuve, Belgium 

Corresponding author.
Abstract

On-body communication technology development requires a better knowledge of antenna radiation and wave propagation along the body, in both near and far fields. Therefore, Green's functions associated with penetrable cylinders are briefly reviewed, considering frequencies at which the body is not much larger than the wavelength and with a particular attention given to the near fields. A unified approach based on current sheets is provided and an acceleration technique is proposed. This is validated with the help of an FDTD software, which also allows the analysis of non-canonical cross-sections. The properties of creeping waves launched by sources parallel and perpendicular to the body are studied, in particular from the point of view of their phase velocity, and a very simple fitting model is proposed. It is also explained how the Green function can be exploited to analyze antennas very efficiently with the help of an integral-equation approach.

The full text of this article is available in PDF format.
Résumé

La technologie de communication corporelle nécessite une meilleure connaissance du rayonnement des antennes et de la propagation le long du corps humain, tant en champs proches qu'en champs lointains. Par conséquent, les fonctions de Green associées aux cylindres pénétrables sont brièvement revues pour des fréquences où le corps n'est pas beaucoup plus grand que la longueur d'onde, avec une attention particulière portée aux champs proches. Une approche unifiée, fondée sur des nappes de courant, est adoptée, et une technique d'accélération est proposée. Ceci est validé à l'aide d'un logiciel FDTD, qui permet aussi l'analyse de sections non canoniques. Les propriétés des ondes rampantes excitées par des sources parallèles et perpendiculaires au corps sont étudiées : en particulier, leur vitesse de phase. Un modèle d'interpolation très simple est proposé. Nous expliquons également comment les antennes en présence du corps peuvent être analysées en exploitant les fonctions de Green via la résolution d'équations intégrales.

The full text of this article is available in PDF format.

Keywords : Body area networks, Creeping waves, Antennas

Mots-clés : Réseaux corporels, Ondes rampantes, Antennes


1  In the following, the z superscript will be omitted in   and  .
2  Hence, deriving w.r.t. z and ϕ amounts to multiplying by   and  , respectively.
3  Each node has a Dual Intel Xeon E5405 (Quad Core 2.0 GHz) central processing unit (CPU). There are 128 cores and 512 GB memory in total providing 4 GB at each processor
4  As Collin explained in [[53]], the Norton wave is not – strictly speaking – a surface wave, but it nonetheless corresponds to what is usually referred to as the surface-wave field. The Zenneck wave appears as an eigensolution for propagation with a complex wavenumber along the interface when one of the media is lossy; the Norton wave corresponds to the asymptotic behavior of the total fields when such an interface is illuminated by a normal current source.
5  The reflection coefficient is calculated as  , where Z is the complex antenna impedance.
6  In short, expressing differential operators in cylindrical coordinates [[62]] and denoting   as  ,   produces  , which appears in  . A replacement produces  , without the   term.
7  This can be verified by noting that in [[24]], a   factor is missing in (8) and (9) and that, in (10),  , by virtue of the equation that defines Bessel's functions.


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