Transcript NRL Radio Propagation at 90 GHz RADAR DIVISION Vilhelm Gregers-Hansen

NRL
RADAR DIVISION
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
1
NRL
07/12/2000
Overview

Propagation effects and 90 GHz

Dry air atmosphere

Water vapor

Fog and clouds

Rain

Other effects

Summary
FCC Forum 90 GHz.PPT
2
NRL
Propagation Effects

Molecular absorption in gas



Extinction due to particles

Clouds, fog

Rain, snow, hail

Dust, sand
Refraction


07/12/2000
Oxygen, water vapor
Anomalous propagation
Fading along propagation path
FCC Forum 90 GHz.PPT
3
NRL
Atmospheric Attenuation
Versus Frequency
oxygen & H2O
High Attenuation (>1 dB/km)
Low Attenuation (<1 dB/km)
fog & clouds
W-Band
Ka-Band
0.4- 10 GHz
Microwave
07/12/2000
10-3000 GHz
mm-wave
FCC Forum 90 GHz.PPT
IR
rain
Visible
3000- 1000000 GHz
IR and Visible
4
NRL
07/12/2000
Dry Atmosphere at Low Altitude

Barometric pressure ~ 1013 mB

Temperature -30 to +35 C

Relative humidity RH= 0%

Nitrogen 78%

Oxygen 21%

Other 1%
FCC Forum 90 GHz.PPT
5
Specific Attenuation - g (dB/km)
NRL
Dry Atmosphere Attenuation at
Low Altitude - 1
100
50
20
10
5
2
1
0.5
0.2
0.1
0.05
Dry Air
0.02
0.01
10
07/12/2000
20
40
70 100
200
Frequency - f (GHz)
FCC Forum 90 GHz.PPT
400
7001000
6
Dry Atmosphere Attenuation
Low Altitude - 2
NRL
Specific Attenuation - g (dB/km)
100
50
07/12/2000
20
10
5
2
1
0.5
0.2
0.1
0.05
0.02
0.01
50
Dry Air
60
70
80 90 100 110 120 130 140 150
Frequency - f (GHz)
FCC Forum 90 GHz.PPT
7
NRL
Water Vapor Characterization
Standard Definition:
g/m3

Temperature (T C)

Relative humidity (RH %)
10
RH=100%
What really matters:

1
RH=5%
Water vapor
concentration in g/m3
0.1
-10
07/12/2000
0
10
20
30
40 C
FCC Forum 90 GHz.PPT
8
NRL
Effect of Water Vapor and Oxygen
RH= 50%
Specific Attenuation - g (dB/km)
100
50
T= 40ºC
20
10
5
T= 30ºC
2
1
0.5
T= 0ºC
T= 20ºC
T= 10ºC
0.2
0.1
0.05
Dry Air
0.02
0.01
10
07/12/2000
20
40
70 100
200
Frequency - f (GHz)
400
FCC Forum 90 GHz.PPT
7001000
9
Specific Attenuation Due to
Oxygen and Water Vapor
NRL
Specific Attenuation - g (dB/km)
100
Sea Level (1013 mB)
10
1
T=20ºC and RH=50%
0.1
0.01
T=20ºC and RH=0%
0.001
0
20
40
60
80
100
120
140
160
180
200
Frequency - f (GHz)
07/12/2000
FCC Forum 90 GHz.PPT
10
Attenuation vs. Frequency
50 % Relative Humidity
NRL
Specific Attenuation- g (dB/km)
1.4
1.2
T= 35ºC
1
T= 30ºC
0.8
T= 25ºC
0.6
T= 20ºC
0.4
T= 15ºC
T= 10ºC
T= 5ºC
0.2
T= 0ºC
0
90
91
92
93
94
95
96
97
98
99
100
Frequency - f (GHz)
07/12/2000
FCC Forum 90 GHz.PPT
11
NRL

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
07/12/2000
FCC Forum 90 GHz.PPT
Ref: Kulpa et al, 1979
12
Attenuation Calculated From Persian
Gulf Radiosonde Measurements
NRL
10000
Height - H (m)
94 GHz
1000
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
13
NRL
07/12/2000
Visibility due to Fog
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
14
NRL
Attenuation due to Fog
T=15 C
Specific Attenuation - g (dB/km)
100
50
07/12/2000
20
10
5
Fog 0.1 g/m3
100 m Visibility
& RH=100%
2
1
0.5
H2O
RH=100%
0.2
0.1
0.05
0.02
0.01
10
Dry Air
20
40
70 100
200
Frequency - f (GHz)
FCC Forum 90 GHz.PPT
400
7001000
15
NRL
W-Band Performance in Clouds/ Fog
Specific Attenuation - g (dB/km)
1000
100
10
94 GHz
1
Clouds or Fog 0.1 g/m3
Visibility 50 m
0.1
0.01
10-3
MicroW
mm
10
100
Sub-mm
IR
Visible
10-4
10-5
1
1000
10000
100000 1000000
Frequency - f (GHz)
07/12/2000
FCC Forum 90 GHz.PPT
16
NRL
Rain Characteristics
Basic Definition:

Rain rate r (mm/hr)

Drop size distribution
Meteorology:
07/12/2000

Probability of precipitation at rate r

Height distribution of precipitation

Rain cell diameter

Thunderstorm cell diameter
FCC Forum 90 GHz.PPT
17
NRL
Effect of Rain 2.5, 5 , 10 mm/hr
Specific Attenuation - g (dB/km)
100
50
07/12/2000
20
10
5
10 mm/hr
5 mm/hr
2.5 mm/hr
2
1
0.5
0.2
0.1
0.05
0.02
0.01
10
Dry Air
20
40
70 100
200
Frequency - f (GHz)
FCC Forum 90 GHz.PPT
400
7001000
18
NRL
Rain Attenuation at 95 GHz
Light Rain
Moderate Rain
Heavy Rain
Specific Attenuation - g (dB/km)
6
5
Hor Pol
4
Vert Pol
3
2
Tropics
Temperate
Probability
1
> 1%
0
0
1
1%
2
< 1%
3
4
5
6
7
8
Rain Rate - r (mm/h)
07/12/2000
FCC Forum 90 GHz.PPT
19
NRL
Some References
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
20
NRL
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
21