December 1983 | NTIA Technical Report TR-83-137

An Atmospheric Millimeter Wave Propagation Model

Hans J. Liebe


The neutral atmosphere is characterized for the frequency range from 1 to 300 GHz as a nonturbulent propagation medium. Attenuation and propagation delay effects are predicted from meteorological data sets: pressure, temperature, humidity, suspended particle concentration, and rain rate. The physical data base of the propagation model consists of four terms: (a) resonance information for 30 water vapor and 48 oxygen absorption lines in the form of intensity coefficients and center frequency for each line; (b) a composite (oxygen, water vapor, and nitrogen) continuum spectrum; (c) a hydrosol attenuation term for haze, fog, ,and cloud conditions; and (d) a rain attenuation model. Oxygen lines extend into the mesosphere, where they behave in a complicated manner due to the Zeeman effect. The geomagnetic field strength H is required as an additional input parameter. Each 02 line splits proportionally with H into numerous, sub-lines, which are juxtaposed to form a Zeeman pattern spread over a megahertz scale. Patterns for three main polarization cases are calculated. Detailed examples for model atmospheres provide basic millimeter wave propagation information over the height range 0 to 100 km of the neutral atmosphere.

Keywords: atmospheric attenuation; delay effects; millimeter wave properties of air; propagation model; oxygen Zeeman patterns

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