Fluctuations in Millimeter-Wave Signals Propagated Through Inclement Weather

摘要

This reprint presents results obtained in measuring the effects of inclement weather on the fluctuations in amplitude and phase of millimeter-wave signals propagated through the atmosphere. These measurements were made at frequencies near 116, 140, 173, and 230 GHz at a site near Champaign-Urbana, Illinois, in the community of Flatville, chosen for its exceptional flatness and lack of terrain features that might perturb the atmosphere. It was found that these inclement weather fluctuations are generally smaller than those observed in clear air under sunny conditions, and are also smaller than the corresponding effects observed at visible and near-infrared wavelengths. Typical values of the intensity standard deviation observed (in 20-s intervals) were 1 percent in rain, 0.2 percent in fog, and 1.5-2.5 percent in snow. These results should be compared with results of about 7 percent typical of clear air on sunny days. Typical values of the standard deviation of wavelength angle-of-arrival were 40, 5, 4, and 1 microrad for clear air, snow rain, and fog, respectively. It was also found that rain has the greatest effect on MMW transmission, causing large, slow changes in received signal strength as a function of rain rate. It should also be noted that rain caused the only observed loss of the propagation link, during a thunderstorm in which the rain was as high as 60 mm/h. (jhd-xx)