Title :
Analysis of the effects of water on the ACTS propagation terminal antenna
Author :
Crane, Robert K.
Author_Institution :
Sch. of Meteorol., Oklahoma Univ., Norman, OK, USA
fDate :
7/1/2002 12:00:00 AM
Abstract :
The NASA advanced communications technology satellite (ACTS) propagation experiment was designed to observe the attenuation produced by rain on Earth-satellite paths operating in the Ka-band. Unwanted effects of water on the antenna reflector surface were noted. Wet-antenna attenuation could be attributed to the combined effect of a water layer on the reflector surface and water wetting the feed window surface. A model was developed to calculate the antenna reflector and feed surface water layer thickness values as a function of position on each surface. The thickness values were used to calculate the additional attenuation produced by the water layers as a function of rain rate on the antenna. The wet-antenna-attenuation prediction model was verified by sprayer tests. The goal of the ACTS propagation experiment was to obtain path attenuation statistics, statistics that represent the effects of rain on the Earth-satellite path but not on the antenna itself. The wet-antenna attenuation prediction model was used to remove the effects of water on the antenna from the combined antenna-plus-path attenuation statistics produced by the experiment. The overall efficacy of the model was demonstrated by comparing the corrected path loss statistics from two ACTS propagation experiment sites with earlier COMSTAR path loss measurements made at or near those sites. The empirical distribution functions from both the ACTS and COMSTAR experiments were identical within the expected uncertainty of an empirical annual distribution of attenuation by rain.
Keywords :
electromagnetic wave absorption; electromagnetic wave scattering; microwave propagation; millimetre wave propagation; radomes; rain; reflector antenna feeds; reflector antennas; satellite links; 20.2 GHz; 27.5 GHz; ACTS propagation experiment; COMSTAR path loss measurements; Ka-band; NASA; advanced communications technology satellite; antenna reflector surface; feed window surface; rain attenuation; water; wet antenna attenuation; wet radomes; Antennas and propagation; Attenuation; Feeds; NASA; Predictive models; Propagation losses; Rain; Reflector antennas; Statistical distributions; Statistics;
Journal_Title :
Antennas and Propagation, IEEE Transactions on
DOI :
10.1109/TAP.2002.800701