Antenna beam elevation angle for control of tropospheric interference between space system earth terminals and terrestrial stations

Abstract

High gain antennas, sensitive receivers and high power transmitters which are used at the earth stations of space communications systems complicate the problem of sharing frequencies with other surface services. However, because of the dependence of beyondthe-horizon tropospheric propagation on the scattering angle, it is possible to offset the gain of the terminal antenna by elevating the beam, Early studies of frequency-sharing assumed that the beam of the earth station was elevated "sufficiently" to increase the transmission loss to that which would be obtained if the actual antenna were replaced by an isotropic antenna. This paper studies the question of what constitutes a "sufficient" elevation angle, as described above, for the particular conditions of a smooth earth, 30-foot antenna heights and several combinations of antenna sizes. Some results are also given when there is an elevated horizon at the earth terminal end of the path.1.