Dynamics of the lower atmosphere through analysis of fade characteristics of microwave signals

Abstract

Fade characteristics of 6/7 GHz signal collected over Milmilia, Maopet and Laopani Line-of-sight (LOS) links of Assam valley have been analyzed with supporting meteorological parameters in relation to receive-system dynamics. Statistical analyses of fade rate such as probability of occurrence, cumulative distribution (at 50% probability level) etc. at different temporal situations have been made. The vertical velocity of the atmospheric irregularities leading to signal fluctuations has been calculated from fade durations. Using these velocity component, a model equation relating vertical velocity and fade rate has been framed. A few case studies on particular fade events over Laopani link have been carried out to derive irregularity parameters such as scale size, scattered component and refractivity structure constant C2n. Finally the fade analysis has been used as a tool for interpreting morning time fast fades due to the scattering of signal by high speed (0.3 m/s) small scale dense irregularities, and nocturnal fades through reflection of signal from relatively stable layers.