February 1982 | NTIA Technical Report TR-82-96

Molecular Absorption Test at 35 GHz

Hans J. Liebe

Abstract: This report describes a laboratory experiment which was conducted to find out if the absolute attenuation of a 35 GHz signal by the molecular species H2O2 (hydrogen peroxide), HN03 (nitric acid), N02 (nitrogen dioxide), N2O (nitrous oxide) exceeds a threshold value of 0.2 dB/km for concentrations reaching 500 ppm/vol in 1 atm of air. A resonance spectrometer was operated with a detection sensitivity of 0.1 dB/km to obtain pressure scans of attenuation and refraction for the pure gases at low pressures (< 1 kPa) and for binary mixtures at atmospheric pressures (> 50 kPa) using nitrogen as the inert, loss–free host gas. Model calculations of attenuation over the frequency range 10 to 50 GHz were performed for natural moist air and hot air (< 500 K) under sea level conditions. The measurements of the identified trace gas species produced little (< 0.2 dB/km) additional attenuation.

Keywords: atmospheric attenuation; laboratory measurements; model calculations; trace gas absorption; 3.5 GHz band

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