Accession Number : AD0686664

Title :   ATTENUATION OF MICROWAVE RADIATION FOR PATHS THROUGH THE ATMOSPHERE

Descriptive Note : Interim rept.

Corporate Author : NAVAL RESEARCH LAB WASHINGTON DC

Personal Author(s) : LeFande, R. A.

PDF Url : AD0686664

Report Date : 29 NOV 1968

Pagination or Media Count : 34

Abstract : Microwave radiation is absorbed by atmospheric oxygen and water vapor and is absorbed and scattered by rainfall. The report provides values of these losses in the frequency decade from 10 to 100 GHz for paths through the atmosphere at elevation angles from 0 to 90 degrees. The theoretical expressions for oxygen absorption are assembled in explicit form. The resonant frequencies are taken from published low-pressure measurements, and the entire absorption profile is fitted to published intermediate and atmospheric pressure results, with a constant of proportionality and the absorption resonance line width used as fitting parameters. The absorption line breadth is found to deviate from the accepted linear pressure dependence, increasing approximately as the square root of pressure for pressures above one-half atmospheric. The results of similar analyses of water vapor absorption are assembled and combined with the results of oxygen absorption analyses to obtain the complete absorption coefficients as a function of the atmospheric parameters. The total attenuation due to absorption in the clear atmosphere is computed for a model atmosphere with various water vapor concentrations. Results are provided in graphical form, giving attenuation as a function of frequency and elevation angle. Rough estimates for rain attenuation are made for crude model storms which occur for 1, 0.1, and 0.01 percent of the time. Total values of the attenuation for the model storms and the atmospheric absorption are provided.

Descriptors :   *MICROWAVES, PREDICTIONS, OXYGEN, ATTENUATION, ABSORPTION SPECTRA, RAINFALL, ATMOSPHERES, WATER VAPOR

Subject Categories : Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE