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Origin of multipath fading on a terrestrial microwave link

Origine des Évanouissements par trajets multiples sur les liaisons terrestres hyperfrÉquences

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Abstract

The effects of surface and atmospheric mechanisms involved in the generation of frequency-selective multipath fading have to be investigated to help improve the performance of wide-band digital radio systems on line-of-sight microwave links. In this paper, three typical mechanisms of super-refractive layer formation are simulated: a layer which develops and grows close to the ground level (ground-based layer), a layer which forms close to the ground and then weakens in elevating (rising or elevating layer), and a layer which appears above the antenna heights and grows at this altitude (elevated layer). A ray-tracing program is then used to compute the time response of the propagation channel for each of these three layers. The results are compared with experimental observations and space diversity considerations are also presented.

Résumé

Les effets des mécanismes atmosphériques et de surface conduisant à la présence de trajets multiples, et donc à des affaiblissements sélectifs en fréquence, doivent être étudiés pour améliorer les performances des systèmes numériques à large bande sur faisceaux hertziens hyperfréquences en visibilité. Dans cet article, trois mécanismes typiques conduisant à supraréfraction sont simulés: une couche qui se développe et grandit au niveau du sol (couche basée au sol), une couche qui se forme près du sol et s’affaiblit en prenant de ľaltitude (couche montante), et une couche qui apparaît au-dessus des hauteurs ďantenne et grandit à cette altitude (couche élevée). Un programme de tracé de rayons est ensuite utilisé pour calculer la réponse temporelle du canal de propagation pour chacune de ces trois couches. Les résultats sont comparés avec des observations expérimentales, et des considérations sur ľutilisation ďune technique par diversité ďespace sont aussi présentées.

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Authors and Affiliations

  1. Department of Electrical Engineering, University of Western Ontario, N6A 5B9, London, Canada

    Didier Rana & Alan R. Webster

  2. Centre de recherche en physique de ľenvironnement terrestre et planétaire, Centre national de la recherche scientifique, F-78140, Velizy, France

    Michel Sylvain

Authors
  1. Didier Rana
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  2. Alan R. Webster
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  3. Michel Sylvain
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Rana, D., Webster, A.R. & Sylvain, M. Origin of multipath fading on a terrestrial microwave link. Ann. Télécommun. 48, 557–566 (1993). https://doi.org/10.1007/BF02995491

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  • DOI: https://doi.org/10.1007/BF02995491

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