Jerry D. Hopponen and Hans J. Liebe

Abstract: Prediction of propagation effects (i.e., path attenuation, phase delay, ray bending and medium noise) over the 1 to 300 GHz frequency range through the clear, nonturbulent atmosphere is accomplished by combining a spectroscopic data base with a computer program for two dimensional ray tracing. Interactions between the physical environment and electromagnetic radiation are expressed by a complex refractivity N. The quantity N is a function of frequency, pressure, humidity, and temperature. Spectroscopic data supporting N consist of more than 450 coefficients describing local O₂ and H₂O absorption lines complemented by continuum spectra for dry air and water vapor. Height profiles (up to 80 km) of N-spectra are the basis for calculating propagation effects along a radio path (ground–to–ground, ground-to-aircraft, and ground-to-satellite). The computer model assumes a symmetric, spherically stratified atmosphere without horizontal N gradients. Evaluation of path integrals for radio range, cumulative attenuation, and noise temperature is accomplished in a rapid manner. Various simulated propagation aspects and details of the treatment of the noise integrals are given.

Keywords: millimeter-wave propagation; clear atmosphere; path attenuation and delay; radiances; radio path modeling; ray bending

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