Recommendation ITU-R P.838

This Recommendation provides a method to compute the specific attenuation for rain for use in prediction methods.

Title PDF Latest approved in
Recommendation ITU-R P.838 [PDF] 2005-03
Specific attenuation model for rain for use in prediction methods
Current recommendation version (In force)   Date
Recommendation ITU-R P.838-3 [PDF] 03/2005
Recommendations implemented in ITU-Rpy   Date
Recommendation ITU-R P.838-3 [PDF] 03/2005
Recommendation ITU-R P.838-2 [PDF] 04/2003
Recommendation ITU-R P.838-1 [PDF] 10/1999
Recommendation ITU-R P.838-0 [PDF] 03/1992

Introduction

The specific attenuation \(\gamma_R\) (dB/km) is obtained from the rain rate \(R:math:\) (mm/h) using the power-law relationship:

\[\gamma_R = k R^{\alpha}\]

Values for the coefficients \(k\) and \(\alpha\) are determined as functions of frequency, f (GHz), and this recommendation provides value valid in the range from 1 to 1 000 GHz. The models from Recommendation ITU-R P.838 have been developed from curve-fitting to power-law coefficients derived from scattering calculations:

Module description

itur.models.itu838.change_version(new_version)[source]

Change the version of the ITU-R P.838 recommendation currently being used.

This function changes the model used for the ITU-R P.838 recommendation to a different version.

Parameters:new_version (int) –

Number of the version to use. Valid values are:

  • 3: Activates recommendation ITU-R P.838-3 (03/05) (Current version)
  • 2: Activates recommendation ITU-R P.838-2 (04/03) (Superseded)
  • 1: Activates recommendation ITU-R P.838-1 (10/99) (Superseded)
  • 0: Activates recommendation ITU-R P.838-0 (03/92) (Superseded)
itur.models.itu838.get_version()[source]

Obtain the version of the ITU-R P.838 recommendation currently being used.

Returns:version – Version currently being used.
Return type:int
itur.models.itu838.rain_specific_attenuation_coefficients(f, el, tau)[source]

Compute the values for the coefficients k and α.

A method to compute the values for the coefficients k and α to compute the rain specific attenuation \(\gamma_R\) (dB/km) (dB/km)

Parameters:
  • f (number or Quantity) – Frequency (GHz)
  • el (number, sequence, or numpy.ndarray) – Elevation angle of the receiver points
  • tau (number, sequence, or numpy.ndarray) – Polarization tilt angle relative to the horizontal (degrees). Tau = 45 deg for circular polarization)
Returns:

  • k (number) – Coefficient k (non-dimensional)
  • α (number) – Coefficient α (non-dimensional)

References

[1] Rain height model for prediction methods: https://www.itu.int/rec/R-REC-P.838/en

itur.models.itu838.rain_specific_attenuation(R, f, el, tau)[source]

Compute the specific attenuation γ_R (dB/km) given the rainfall rate.

A method to compute the specific attenuation γ_R (dB/km) from rain. The value is obtained from the rainfall rate R (mm/h) using a power law relationship.

\[\gamma_R = k R^\alpha\]
Parameters:
  • R (number, sequence, numpy.ndarray or Quantity) – Rain rate (mm/h)
  • f (number or Quantity) – Frequency (GHz)
  • el (number, sequence, or numpy.ndarray) – Elevation angle of the receiver points
  • tau (number, sequence, or numpy.ndarray) – Polarization tilt angle relative to the horizontal (degrees). Tau = 45 deg for circular polarization)
Returns:

γ_R – Specific attenuation from rain (dB/km)
Return type:

numpy.ndarray

References

[1] Rain height model for prediction methods: https://www.itu.int/rec/R-REC-P.838/en