Attenuation and Phase Delay of Radio Waves in Air Below 1000 GHZ for Heights 0 to 100 KM
Abstract
Moist air is characterized for the frequency range 10 to 1000 GHz as a nonturbulent propagation medium. The medium is treated as an ensemble of molecules in which spectral features of water vapor and oxygen constitute the main absorbers. An adequate permanent spectroscopic data base consists of three parts: (1) resonance information for 30 H2O lines between 22 and 1097 GHz and 44 O2 lines between 50 and 834 GHz in the form of intensity coefficients and center frequency for each line; (2) an empirical water vapor continuum spectrum; and (3) a liquid water attenuation term for haze and cloud conditions. The overlap problem of the 60 GHz oxygen band is taken into account. The data base is applied in a dual computer program to calculate and to plot attenuation rates (dB/km), refractivity (ppm), and refractive dispersion (ppm) throughout the neutral atmosphere. The first part covers the hydrosphere (i.e., 0 to 20 km) and requires pressure, temperature, and relative humidity as input data. Part two addresses isolated line behavior over the height range 20 to 100 km, wherein the geomagnetic field strength H is an additional input parameter due to the Zeeman effect of the O2 molecules. Each oxygen line splits proportional with H into numerous sub-lines, which superimpose to form a Zeeman pattern spread over a megahertz scale and exhibiting a shape that depends very much upon polarization and orientation of the interacting radiation. Patterns of three main polarization cases are considered. The unified treatment is central to radio wave propagation problems in the neutral atmosphere up to 1000 GHz. The formulation is in engineering terms, fully traceable, and does not include quantum mechanical complications. Various typical examples for a model atmosphere demonstrate the utility of the approach, provide new information, and underline the serious role that water vapor plays above 150 GHz.
Document Details
- Document Type
- Technical Report
- Publication Date
- Aug 17, 1981
- Accession Number
- ADA105931
Entities
People
- Hans J. Liebe