December 1984 | NTIA Technical Report TR-84-169
Evan J. Dutton; Francis K. Steele
Abstract: In the presence of rain, millimeter–wave propagation is acutely sensitive to the distribution of raindrop sizes along a given propagation link. This report analyzes the variability of rain attenuation prediction at microwave/millimeter wave frequencies caused from the variation of measured raindrop–size distribution data. The results show a considerable need for better and more extensive dropsize distribution data, both in time and geography. After searching for potential solutions, the report discusses the historical development of raindrop distribution measurement methodology, including direct measurement techniques, but with emphasis on indirect, or remote sensing, multiple frequency techniques. These latter techniques are carefully scrutinized, with the conclusion that some information derived separately from the techniques is usually necessary to successful usage of the techniques. Some concluding observations are then made for the selection of an appropriate remote-sensing technique for the improved determination of path-averaged raindrop–size distributions.
Keywords: millimeter waves; raindrop-size distributions; annual variability; attenuation coefficients; multiple frequency techniques; prediction variability
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