Characteristics of fading on low-elevation angle earth-space paths with concurrent rain attenuation and scintillation

Signal-level variations on Ku-band low-elevation earth-space paths, where large signal fades due to rain and tropospheric scintillations sometimes occur simultaneously, are examined. The difference in the amplitude variation rate for rain attenuation and scintillation fading is used to extract the effects of the two phenomena individually from raw data with the aid of a filtering technique. Characteristics of signal fading during rain are discussed on the basis of the analysis. It is shown that the decrease of signal level due to scintillation is much smaller than that due to rain attenuation, particularly for time percentages below 0.1 percent. However, for time percentages above about 1 percent, the effect of scintillation becomes dominant and no longer negligible, particularly for low-margin systems operating at low elevation angles.