ITU-R - International Telecommunication Union/ITU Radiocommunication Sector
适用范围
Introduction The fixed service and the Earth exploration-satellite (EES) passive and space research (passive) services have coprimary allocations in the bands 50.2-50.4 GHz and 54.25-58.2 GHz. The purpose of this Annex is to review the suitability of these allocations and@ where necessary@ to develop limitations to be applied to the fixed service to ensure adequate protection of passive remote sensors. The oxygen absorption in the frequency ranges of interest varies considerably@ with a large number of absorption lines@ around 60 GHz. The level of absorption used in the sharing studies has been calculated from Recommendation ITU-R P.676. It will be shown that the level of absorption has an important effect on the feasibility of sharing. Figure 1 shows the total absorption on a vertical path from Earth-to-space. The absorption on the ground-space path is reduced as the height of ground above sea level is increased. Fixed link transmitters could operate from locations at a range of altitudes. Throughout this Annex@ as a conservative estimate@ it is assumed that fixed service transmitters are at 1 000 m above sea level. At the relatively high frequencies of interest here@ indirect propagation effects can be a significant propagation mechanism. As a worst case representative of indirect propagation mechanisms@ the studies have considered reflection from building roof tops.