The depolarization effects of Earth-Space link at MMW Bands
The depolarization effects of Earth-Space link at MMW Bands and their mechanisms are analysed. The models to evaluate XPD induced by clear atmosphere, rain, ice crystals, snow, sand-dust storm and ionized layer are summarized and analysed. The methods to calculate total XPD including the influence of transmitting antenna are discussed. The results given in this paper are important for frequency resue and depolarization MIMO techniques.
La réutilisation des fréquences en polarisations croisées avec diversité d’espace sur 50 km a 7 GHz
AnalyseL’auteur présente les résultats de mesures de variations du découplage de polarisation obtenues sur une liaison hertzienne de 50 km fonctionnant à 7 GHz, en période d’affaiblissements par trajets multiples. Après avoir rappelé l’influence d’un brouilleur sur un signal modulé par déplacement de phase, il donne des résultats de calcul de la qualité d’un canal numérique en démodulation différentielle, sur une liaison qui utiliserait les deux polarisations rectilignes à la même fréquence. La diversité optimale, ou avec seuil de commutation, améliore la qualité d’une liaison fonctionnant en double polarisation.AbstractThe author present experimental data describing the statistics of 7 GHz polarization discrimination during multipath fading obtained on a 50 km path. He gives a formulation of cross polarization interference on aPSKsignal, and calculatesQDPSKchannel quality on a link with dual polarized frequency. Switching space diversity, without or with threshold improve dual polarization radio link quality.
Proliferative kidney disease: first reported outbreak in North America
Abstract. Proliferative kidney disease (PKD) was diagnosed in rainbow trout, Salmo gairdneri Richardson, at the Hagerman, Idaho, State Fish Hatchery. Wild fish from Riley Creek, one of the hatchery water supplies, were infected with PKD organisms. Clinical signs, gross pathology and histopathology of affected fish were typical of those reported for PKD in salmonids from European hatcheries. In addition to lesions normally seen, we observed a severe vasculitis and occlusion of renal and hepatic vessels. Ultrastructure of the PKD organism and possible inclusion body production sites are described. The disease outbreak was complicated by the presence of other infectious diseases. This is the first recorded outbreak of PKD in North America.