Radio Propagation at 90 GHz

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Presentation transcript:

Radio Propagation at 90 GHz Vilhelm Gregers-Hansen Radar Division Naval Research Laboratory Presented at FCC Forum: “New Horizons : 90 GHz Technologies” July 14, 2000 07/12/2000 FCC Forum 90 GHz.PPT

Overview Propagation effects and 90 GHz Dry air atmosphere Water vapor Fog and clouds Rain Other effects Summary 07/12/2000 FCC Forum 90 GHz.PPT

Propagation Effects Molecular absorption in gas Oxygen, water vapor Extinction due to particles Clouds, fog Rain, snow, hail Dust, sand Refraction Anomalous propagation Fading along propagation path 07/12/2000 FCC Forum 90 GHz.PPT

Atmospheric Attenuation Versus Frequency oxygen & H2O High Attenuation (>1 dB/km) Low Attenuation (<1 dB/km) fog & clouds IR Visible W-Band rain Ka-Band 0.4- 10 GHz 10-3000 GHz 3000- 1000000 GHz Microwave mm-wave IR and Visible 07/12/2000 FCC Forum 90 GHz.PPT

Dry Atmosphere at Low Altitude Barometric pressure ~ 1013 mB Temperature -30 to +35 C Relative humidity RH= 0% Nitrogen 78% Oxygen 21% Other 1% 07/12/2000 FCC Forum 90 GHz.PPT

Dry Atmosphere Attenuation at Low Altitude - 1 100 50 20 10 5 2 Specific Attenuation - g (dB/km) 1 0.5 0.2 0.1 0.05 Dry Air 0.02 0.01 10 20 40 70 100 200 400 700 1000 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Dry Atmosphere Attenuation Low Altitude - 2 100 50 20 10 5 2 1 Specific Attenuation - g (dB/km) 0.5 0.2 0.1 0.05 Dry Air 0.02 0.01 50 60 70 80 90 100 110 120 130 140 150 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Water Vapor Characterization Standard Definition: Temperature (T C) Relative humidity (RH %) g/m3 10 What really matters: RH=100% Water vapor concentration in g/m3 1 RH=5% 0.1 -10 0 10 20 30 40 C 07/12/2000 FCC Forum 90 GHz.PPT

Effect of Water Vapor and Oxygen RH= 50% 100 T= 40ºC T= 30ºC T= 20ºC T= 10ºC T= 0ºC 50 20 10 5 2 Specific Attenuation -  (dB/km) 1 0.5 0.2 0.1 0.05 Dry Air 0.02 0.01 10 20 40 70 100 200 400 700 1000 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Specific Attenuation Due to Oxygen and Water Vapor 100 Sea Level (1013 mB) 10 1 Specific Attenuation - g (dB/km) T=20ºC and RH=50% 0.1 0.01 T=20ºC and RH=0% 0.001 20 40 60 80 100 120 140 160 180 200 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Attenuation vs. Frequency 50 % Relative Humidity 1.4 1.2 T= 35ºC 1 T= 30ºC 0.8 Specific Attenuation- g (dB/km) T= 25ºC 0.6 T= 20ºC 0.4 T= 15ºC T= 10ºC 0.2 T= 5ºC T= 0ºC 90 91 92 93 94 95 96 97 98 99 100 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Water Vapor Contents vs Altitude Water vapor content decreases rapidly with altitude due to decreasing temperature (4-6 ºC/km) Important Range at 90 GHz Ref: Kulpa et al, 1979 07/12/2000 FCC Forum 90 GHz.PPT

Attenuation Calculated From Persian Gulf Radiosonde Measurements 10000 94 GHz 1000 Height - H (m) 100 USS Arkansas CG-34 August 24, 1991 10 0.001 0.01 0.1 1 Specific Attenuation - g (dB/km) 07/12/2000 FCC Forum 90 GHz.PPT

Visibility due to Fog 07/12/2000 FCC Forum 90 GHz.PPT Density of fog usually described in terms of visibility range Related to water content in g/m3 Particle size affects attenuation Radiation fog : Cooling after sunset Advection fog: Humid air and low surface temperature 07/12/2000 FCC Forum 90 GHz.PPT

Attenuation due to Fog T=15 C 100 50 20 10 Fog 0.1 g/m3 100 m Visibility & RH=100% 5 2 H2O RH=100% 1 Specific Attenuation - g (dB/km) 0.5 0.2 0.1 0.05 Dry Air 0.02 0.01 10 20 40 70 100 200 400 700 1000 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

W-Band Performance in Clouds/ Fog 1000 (dB/km) 100 10 g 1 94 GHz Clouds or Fog 0.1 g/m3 Visibility 50 m 0.1 Specific Attenuation - 0.01 10 -3 MicroW mm Sub-mm IR Visible 10 -4 -5 10 1 10 100 1000 10000 100000 1000000 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Rain Characteristics Basic Definition: Meteorology: Rain rate r (mm/hr) Drop size distribution Probability of precipitation at rate r Height distribution of precipitation Rain cell diameter Thunderstorm cell diameter Meteorology: 07/12/2000 FCC Forum 90 GHz.PPT

Effect of Rain 2.5, 5 , 10 mm/hr 100 50 20 10 10 mm/hr 5 5 mm/hr 2 2.5 mm/hr 1 Specific Attenuation - g (dB/km) 0.5 0.2 0.1 0.05 Dry Air 0.02 0.01 10 20 40 70 100 200 400 700 1000 Frequency - f (GHz) 07/12/2000 FCC Forum 90 GHz.PPT

Rain Attenuation at 95 GHz Light Rain Moderate Rain Heavy Rain 6 5 Hor Pol 4 Vert Pol Specific Attenuation - g (dB/km) 3 Temperate Tropics 2 1 Probability > 1% 1% < 1% 1 2 3 4 5 6 7 8 Rain Rate - r (mm/h) 07/12/2000 FCC Forum 90 GHz.PPT

Some References 07/12/2000 FCC Forum 90 GHz.PPT R.K. Crane, Electromagnetic Wave Propagation Through Rain, John Wiley. L.J. Ippolito, “Propagation Effects Handbook for Satellite Systems Design”, NASA Reference Publication 1082(04), 1989. H.J. Liebe, “Millimeter-Wave Properties of the Atmosphere: Laboratory Studies and Propagation Modeling”, US Department of Commerce, NTIA Report 87-224, Oct. 1987. S.M. Kulpa and E.A. Brown, “Near-Millimeter Wave Technology Base Study, Volume I : Propagation and Target/Background Characteristics”, Report HDL-SR-79-8, US Army Materiel Development and Readiness Command and Defense Advanced Project Agency, Nov. 1979 (Approved for public release). H.J. Liebe, G.A. Hufford, and M.G. Cotton, “Propagation modeling of moist air and suspended water/ice particles at frequencies below 1000 GHz”, AGARD Meeting on Atmospheric Propagation Effects through Natural and Man-Made Obscurants for Visible to MM-Wave Radiation, May 1993. 07/12/2000 FCC Forum 90 GHz.PPT

Summary Standard dry atmosphere has a small effect at 90 GHz High humidity at elevated temperatures introduces significant loss (up to 1 dB/km) but only at low altitude. Higher elevation paths suffer loss of only a few dB Effects of fog and clouds quite modest Rain is the most important factor in the design of 90 GHz communication and radar systems 07/12/2000 FCC Forum 90 GHz.PPT