NTIA Report TR-87-224

Millimeter-Wave Properties of the Atmosphere: Laboratory Studies and Propagation Modeling

October 1987

Hans J. Liebe and Donald H. Layton

Abstract: Laboratory measurements have been performed at 138 GHz of water vapor attenuation ax for pure vapor (H2O) and its mixtures with air, nitrogen (N2), oxygen (O2), and Argon (Ar). Temperatures ranged from 8 to 43°C, relative humidities from 0 to 95% and total pressures reached 1.5 atm. A computer-controlled resonance spectrometer was employed. The results are interpreted in terms of underlying absorption mechanisms. Broadening efficiencies m of mixtures H2O + N2, O2, Ar agree among themselves with those measured within cores of the 22 and 183 GHz H2O absorption lines. The m-factors are applied to predict what share al of the total ax results from the complete pressure-broadened H2O spectrum. A substantial amount of the self-broadening term proportional to the square of vapor pressure is left unaccounted. The negative temperature coefficient of the excess absorption is consistent with a dimer (H2O)2 model. An empirical formulation of the experimental findings is incorporated into the parametric propagation model MPM that utilizes a local (30x H2O, 48x O2) line base to address frequencies up to 1000 GHz. Details of MPM are given in two Appendixes. Predictions of moist air attenuation and delay by means of the revised MPM program generally compare favorably with reported (10 - 430 GHz) data from both field and laboratory experiments.

Keywords: atmospheric attenuation and delay; laboratory studies of moist air attenuation; millimeter/submillimeter-wave spectral range; propagation program MPM; radio path data

• Title Page; Contents; List of Figures

• Chapter 1, Introduction

• Chapter 2, DP and DS Interference, pages 3-6
• Chapter 2, DP and DS Interference, pages 7-10 (7.5 MB)
• Chapter 2, DP and DS Interference, pages 11-16

• Chapter 3, Atmospheric Propagation Model MPM (6.5 MB)

• Chapter 4, Experimental-versus-Model (MPM) Data (5.6 MB)

• Chapter 5, Conclusions, & Chapter 6, Acknowledgments

• Chapter 7, References

• Appendix A, The Refractive Index of the Neutral Atmosphere for Frequencies up to 1000 GHz, pages 45-52 (8.7 MB)
• Appendix A, The Refractive Index of the Neutral Atmosphere for Frequencies up to 1000 GHz, pages 53-60 (8.4 MB)
  
  
• Appendix B, Printout of MPM-N Program for Version A (Frequency Profiles), pages 61-68 (8.5 MB)
• Appendix B, Printout of MPM-N Program for Version A (Frequency Profiles), pages 69-74 (7.5 MB)

Disclaimer: Certain commercial equipment, components, and software are identified in this report to specify adequately the technical aspects of the reported results. In no case does such identification imply recommendation or endorsement by the National Telecommunications and Information Administration, nor does it imply that the equipment or software identified is necessarily the best available for the particular application or uses.

For technical information concerning this report, contact:
Michael Cotton, Electronics Engineer
Institute for Telecommunication Sciences
Voice: (303) 497-7346
mcotton@its.bldrdoc.gov