Validity of the CCIR amplitude scintillation model for satellite uplink and downlink communication links with reference to small terminal operation at EHF

Amplitude scintillation´s on satellite communication downlinks are well characterized by the CCIR scintilation model which is now defined in the recommendations of the ITU-R PN.618-3. However amplitude scintillations also occur on uplink paths, for which an established analytical model appears not to exist. This paper applies weak scattering theory to up and downlink scattering geometry´s and includes the effects of transmit and receive antenna apertures. Relationships are derived relating the observed uplink scintillation characteristics to those predicted by the CCIR downlink model. Theory predicts that uplink scintillations could be more severe than those on a downlink at the same frequency. These results are particularly relevant at EHF where amplitude scintillations on slant paths can be several dB´s peak, yet rain fade margins must be constrained to 10 to 15 dB in order for the communication system to be economically practical.