ITU-R RS.1259 PDF

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.