A Study on Time Variation of Rain Attenuation Characteristics for the Kind of Rain Fronts in Ka Band Satellite Communications

摘要

This study presents detailed attenuation characteristics of the Ka-band satellite signal levels observed at 1 sec interval at Osaka Electro-Communication University in Neyagawa, Osaka, from 1997 to 2007. Long-term statistics of the duration time and the fade slope are in fairly good agreement with the ITU-R predictions. In more detail, however, the cumulative probabilities of the duration time become comparatively higher in the typhoon and stationary front events as the duration time increases, while the distribution of the fade slope becomes wider in the cold front events for any threshold levels. These characteristics should be considered for better statistical predictions in Japan. Spectral analysis of the attenuation fluctuation reveals that the spectral components of the rain attenuation are confined in a frequency range of less than 0.1 Hz, i.e., in a time scale of more than 10 sec. According to the rain types, however, there seems to be no clear difference in the slope of each spectral density, indicating similar spectral components for any rain types. This suggests that the difference in the amplitude should be a main cause of the difference in the fade slope statistics for the rain types.