# Presentation: 112227

## 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***

- FCC Forum 90 GHz.PPT

- 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

- 07/12/2000

## 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**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Atmospheric AttenuationVersus Frequency

**0.4- 10 GHz**

**3000- 1000000 GHz**

**10-3000 GHz**

**Microwave**

**mm-wave**

**IR and Visible**

**IR**

**Visible**

***W-Band***

***Ka-Band***

***High Attenuation ******(>1 dB/km)***

***Low Attenuation ******(<1 dB/km)***

**oxygen & H****2****O**

**rain**

**fog & clouds**

- FCC Forum 90 GHz.PPT

- 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

- 07/12/2000

## Dry Atmosphere Attenuation atLow Altitude - 1

**10**

**20**

**40**

**70**

**100**

**200**

**400**

**700**

**1000**

**0.01**

**0.02**

**0.05**

**0.1**

**0.2**

**0.5**

**1**

**2**

**5**

**10**

**20**

**50**

**100**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**Dry Air**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Dry Atmosphere AttenuationLow Altitude - 2

**50**

**60**

**70**

**80**

**90**

**100**

**110**

**120**

**130**

**140**

**150**

**0.01**

**0.02**

**0.05**

**0.1**

**0.2**

**0.5**

**1**

**2**

**5**

**10**

**20**

**50**

**100**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**Dry Air**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Water Vapor Characterization

**Temperature (T  C)**
**Relative humidity (RH %)**

***Standard Definition:***

**Water vapor concentration in g/m3**

***What really matters:***

**-10      0      10     20     30     40   C**

**10**

**1**

**0.1**

**g/m****3**

**RH=100%**

**RH=5%**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Effect of Water Vapor and Oxygen

**10**

**20**

**40**

**70**

**100**

**200**

**400**

**700**

**1000**

**0.01**

**0.02**

**0.05**

**0.1**

**0.2**

**0.5**

**1**

**2**

**5**

**10**

**20**

**50**

**100**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**Dry Air**

**T= 40oC**
**T= 30oC**
**T= 20oC**
**T= 10oC**
**T=  0oC**

**RH= 50%**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Specific Attenuation Due toOxygen and Water Vapor

**0.001**

**0.01**

**0.1**

**1**

**10**

**100**

**0**

**20**

**40**

**60**

**80**

**100**

**120**

**140**

**160**

**180**

**200**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**T=20oC and RH=50%**

**T=20oC and RH=0%**

**Sea Level (1013 mB)**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Attenuation vs. Frequency50 % Relative Humidity

***Attenuation vs. Frequency******50 % Relative Humidity***

**0**

**0.2**

**0.4**

**0.6**

**0.8**

**1**

**1.2**

**1.4**

**90**

**91**

**92**

**93**

**94**

**95**

**96**

**97**

**98**

**99**

**100**

**Frequency - f  (GHz)**

**Specific Attenuation- ********(dB/km)**

**T= 35****oC**

**T= 30oC**

**T= 25oC**

**T= 20oC**

**T= 15oC**

**T= 10oC**

**T= 5oC**

**T= 0oC**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## 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 **

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Attenuation Calculated From Persian Gulf Radiosonde Measurements

***Attenuation Calculated From Persian Gulf Radiosonde Measurements***

**0.001**

**0.01**

**0.1**

**1**

**Specific Attenuation -  ******** (dB/km)**

**10**

**100**

**1000**

**10000**

**Height - H (m)**

**USS Arkansas CG-34**
**August 24, 1991**

**94 GHz**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Visibility due to Fog

**Density of fog usually described in terms of visibility range**
**Related to water content in g/m****3**
**Particle size affects attenuation**
**Radiation fog : Cooling after sunset**
**Advection fog: Humid air and low surface temperature**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Attenuation due to Fog

**10**

**20**

**40**

**70**

**100**

**200**

**400**

**700**

**1000**

**0.01**

**0.02**

**0.05**

**0.1**

**0.2**

**0.5**

**1**

**2**

**5**

**10**

**20**

**50**

**100**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**T=15 C**

**H****2****O**
**RH=100%**

**Fog 0.1 g/m3**
**100 m Visibility**
**& RH=100%**

**Dry Air**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## W-Band Performance in Clouds/ Fog

***W-Band Performance in Clouds/ Fog***

**1**

**10**

**100**

**1000**

**10000**

**100000**

**1000000**

**Frequency - f (GHz)**

**10**

**-5**

**10**

**-4**

**10**

**-3**

**0.01**

**0.1**

**1**

**10**

**100**

**1000**

**Specific Attenuation -**

****

**(dB/km)**

**mm**

**Sub-mm**

**IR**

**Visible**

**Clouds or Fog  0.1 g/m****3**
**Visibility  50 m**

**MicroW**

**94 GHz**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Rain Characteristics

**Rain rate r (mm/hr)**
**Drop size distribution**
**Probability of precipitation at rate r**
**Height distribution of precipitation**
**Rain cell diameter**
**Thunderstorm cell diameter**

***Basic Definition:***

***Meteorology:***

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Effect of Rain 2.5, 5 , 10 mm/hr

**10**

**20**

**40**

**70**

**100**

**200**

**400**

**700**

**1000**

**0.01**

**0.02**

**0.05**

**0.1**

**0.2**

**0.5**

**1**

**2**

**5**

**10**

**20**

**50**

**100**

**Frequency - f (GHz)**

**Specific Attenuation - ******** (dB/km)**

**10 mm/hr**

**5 mm/hr**

**2.5 mm/hr**

**Dry Air**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## Rain Attenuation at 95 GHz

***Rain Attenuation at 95 GHz***

**0**

**1**

**2**

**3**

**4**

**5**

**6**

**7**

**8**

**0**

**1**

**2**

**3**

**4**

**5**

**6**

**Rain Rate - r (mm/h)**

**Specific Attenuation - ******** (dB/km)**

**Hor Pol**

**Vert Pol**

**Heavy Rain**

**Light Rain**

***1%***

**Tropics**

**Temperate**

***> 1%***

***< 1%***

**Moderate Rain**

***Probability***

- FCC Forum 90 GHz.PPT

- 07/12/2000

## 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.**

- FCC Forum 90 GHz.PPT

- 07/12/2000

## 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**

- FCC Forum 90 GHz.PPT

- 07/12/2000