p618PropagationLosses

Calculate Earth-space propagation losses, cross-polarization discrimination, and sky noise temperature

Syntax

[pl,xpd,tsky] = p618PropagationLosses(p618cfg)

[pl,xpd,tsky] = p618PropagationLosses(p618cfg,Name,Value)

Description

[pl,xpd,tsky] = p618PropagationLosses(p618cfg) returns Earth-space propagation losses pl, cross-polarization discrimination xpd, and sky noise temperature tsky, as defined in the ITU-R P.618-14 recommendation [1]. p618cfg specifies the P.618 configuration parameters.

This function requires a MAT file with digital maps from International Telecommunication Union (ITU) documents. If it is not available on the path, download and uncompress the data file from https://www.mathworks.com/supportfiles/spc/P618/ITURP618v14DigitalMaps.tar.gz to a location on the MATLAB^® path.

Note

If you are using MATLAB in version R2025b or earlier, refer to the Tips section for instructions on how to run the examples by using ITU-R P.618-13.

[pl,xpd,tsky] = p618PropagationLosses(p618cfg,Name,Value) specifies additional options using one or more name-value arguments.

Examples

Calculate Propagation Losses, Cross-Polarization Discrimination, and Sky Noise Temperature

This example requires a MAT file with digital maps from ITU documents. If the MAT file is not available on the path, execute the following commands to download and extract it.

matFile = exist('iturp618v14Maps.mat','file');
if ~matFile
    if ~exist('ITURP618v14DigitalMaps.tar.gz','file')
        url = 'https://www.mathworks.com/supportfiles/spc/P618/ITURP618v14DigitalMaps.tar.gz';
        websave('ITURP618v14DigitalMaps.tar.gz',url)
        untar('ITURP618v14DigitalMaps.tar.gz')
    else
        untar('ITURP618v14DigitalMaps.tar.gz')
    end
    addpath(cd)
end

Create a default P.618 configuration object.

cfg = p618Config;

Specify the time percentage of excess for the rain attenuation per annum as 0.01 and the time percentage of excess for the total attenuation per annum as 0.001.

cfg.RainAnnualExceedance = 0.01;
cfg.TotalAnnualExceedance = 0.001;

Calculate the propagation losses, cross-polarization discrimination, and sky noise temperature.

[pl,xpd,tsky] = p618PropagationLosses(cfg)

pl = struct with fields:
    Ag: 0.2278
    Ac: 0.2473
    Ar: 6.7981
    As: 0.2633
    At: 15.2643

xpd = 
32.8876

tsky = 
266.8455

Calculate Earth-Space Propagation Losses Using Name-Value Pair Arguments

This example requires a MAT file with digital maps from ITU documents. If the MAT file is not available on the path, execute the following commands to download and extract it.

matFile = exist('iturp618v14Maps.mat','file');
if ~matFile
    if ~exist('ITURP618v14DigitalMaps.tar.gz','file')
        url = 'https://www.mathworks.com/supportfiles/spc/P618/ITURP618v14DigitalMaps.tar.gz';
        websave('ITURP618v14DigitalMaps.tar.gz',url)
        untar('ITURP618v14DigitalMaps.tar.gz')
    else
        untar('ITURP618v14DigitalMaps.tar.gz')
    end
    addpath(cd)
end

Create a P.618 configuration object with a signal frequency of 20 GHz.

cfg = p618Config(Frequency=20e9);

Specify the surface water vapor density as 2.8$\frac{g}{m^3}$, the total columnar content of the cloud liquid water as 1.4 $\frac{\text{kg}}{m^2}$, and the median value of the wet surface refractivity as 1.2. Set the earth station height as 0.5 km. Calculate the Earth-space propagation losses.

pl =  p618PropagationLosses(cfg,StationHeight=0.5, ...
                            WaterVaporDensity=2.8, ...
                            TotalColumnarContent=1.4, ...
                            WetSurfaceRefractivity=1.2)

pl = struct with fields:
    Ag: 0.8097
    Ac: 0.8986
    Ar: 0.8907
    As: 0.1372
    At: 2.4911

Calculate Propagation Losses in Light Rainfall

This example requires a MAT file with digital maps from ITU documents. If the MAT file is not available on the path, execute the following commands to download and extract it.

matFile = exist('iturp618v14Maps.mat','file');
if ~matFile
    if ~exist('ITURP618v14DigitalMaps.tar.gz','file')
        url = 'https://www.mathworks.com/supportfiles/spc/P618/ITURP618v14DigitalMaps.tar.gz';
        websave('ITURP618v14DigitalMaps.tar.gz',url);
        untar('ITURP618v14DigitalMaps.tar.gz');
    else
        untar('ITURP618v14DigitalMaps.tar.gz');
    end
    addpath(cd);
end

Create a P.618 configuration object that occupies a signal frequency of 20 GHz.

cfg = p618Config(Frequency=20e9);

Calculate the propagation losses in a light rainfall of 1 mm/hr with an earth station height of 0.75 km.

pl =  p618PropagationLosses(cfg,RainRate=1,StationHeight=0.75)

pl = struct with fields:
    Ag: 0.7170
    Ac: 0.4763
    Ar: 0.0177
    As: 0.3187
    At: 1.0361

Calculate Gain-to-Noise Temperature Versus Elevation Angle

Use the ITU-R P.618 propagation loss model to calculate a satellite antenna gain-to-noise temperature ratio (G/T) value as a function of elevation angle. As the elevation angle increases, the noise temperature decreases because the received signal has traversed less atmosphere than at lower elevation angles.

This example requires a MAT file with digital maps from ITU documents. If the MAT file is not available on the path, execute the following commands to download and untar it.

matFile = exist('iturp618v14Maps.mat','file');
if ~matFile
    if ~exist('ITURP618v14DigitalMaps.tar.gz','file')
        url = 'https://www.mathworks.com/supportfiles/spc/P618/ITURP618v14DigitalMaps.tar.gz';
        websave('ITURP618v14DigitalMaps.tar.gz',url)
        untar('ITURP618v14DigitalMaps.tar.gz')
    else
        untar('ITURP618v14DigitalMaps.tar.gz')
    end
    addpath(cd)
end

Create a vector of elevation angles to analyze, and specify the attributes of a parabolic dish antenna.

elAngle = 5:5:90; % Elevation angle of antenna boresight pointing, in degrees

% Define circular aperture antenna properties. Assume a parabolic dish.
antDiam = 5.0;    % Antenna diameter, in meters
antEff = 0.6;     % Antenna efficiency, in range (0, 1]
freq = 28e9;      % RF frequency, in Hertz
tRcvr = 100;      % Noise temperature of receiving system, in Kelvin

Compute antenna gain at the frequency specified, in decibels relative to an isotropic antenna.

wavelen = physconst("LightSpeed")/freq;
antGain = 10*log10(antEff) + 20*log10((pi*antDiam)/wavelen);  % dBi

Calculate the sky noise temperature tsky at the geographical site over the vector of elevation angles. The location of the geographical site is 40.00 degrees North and -105.23 degrees West.

numElAngles = length(elAngle);
tSky = zeros(1,numElAngles);
for idxElevation = 1:numElAngles
  cfg = p618Config(Frequency=freq, ...                    % Hz
        ElevationAngle=elAngle(idxElevation), ...         % degrees
        Latitude=40.00, ...                               % degrees North
        Longitude=-105.23, ...                            % degrees West
        TotalAnnualExceedance=1.0, ...                    % percentage
        PolarizationTiltAngle=45, ...                     % degrees
        AntennaDiameter=antDiam, ...                      % meters
        AntennaEfficiency=antEff);                       % (0,1]
  [~,~,tSky(idxElevation)] = p618PropagationLosses(cfg);
end

Calculate the G/T value in decibels per Kelvin.

gT = antGain - 10*log10(tRcvr + tSky);  % G/T
plot(elAngle,gT)
title("G/T vs. Elevation Angle")
xlabel("Elevation Angle (degrees)")
ylabel("G/T (dB/K)")
grid on

Input Arguments

p618cfg — P.618 configuration

p618Config object

P.618 configuration required for the calculation of the propagation losses, cross-polarization discrimination, and sky noise temperature, specified as a p618Config object.

Name-Value Arguments

Specify optional pairs of arguments as Name1=Value1,...,NameN=ValueN, where Name is the argument name and Value is the corresponding value. Name-value arguments must appear after other arguments, but the order of the pairs does not matter.

Before R2021a, use commas to separate each name and value, and enclose Name in quotes.

Example: StationHeight=1.5 specifies the Earth station height as 1.5 km.

StationHeight — Height of Earth station

scalar

Height of the Earth station above the mean sea level in km, specified as the comma-separated pair consisting of StationHeight and a scalar. The maximum supported value is 10. If the local data is not available as an input, the function uses the digital maps provided in ITU-R P.1511 section 1, Annex 1 [3] to obtain the station height value.

Data Types: double | single

Temperature — Temperature of Earth surface

scalar

Temperature of the Earth surface in kelvin, specified as the comma-separated pair consisting of Temperature and a scalar. This argument represents the surface temperature corresponding to GasAnnualExceedance in an average year, at the specified location. You can derive the value from local measurement or obtain from the integrated digital maps provided in Recommendation ITU-R P.2145.

Data Types: double | single

Pressure — Total pressure at Earth surface

scalar

Total pressure at the Earth surface in hPa, specified as the comma-separated pair consisting of Pressure and a scalar. This argument represents the total barometric surface pressure corresponding to GasAnnualExceedance in an average year, at the specified location. You can derive the value from local measurement or obtain from the integrated digital maps provided in Recommendation ITU-R P.2145.

Data Types: double | single

WaterVaporDensity — Surface water vapor density

scalar

Surface water vapor density in g/m³, specified as the comma-separated pair consisting of WaterVaporDensity and a scalar. This argument represents the surface water vapor density corresponding to GasAnnualExceedance in an average year, at the specified location. You can derive the value from local measurement or obtain from the integrated digital maps provided in Recommendation ITU-R P.2145.

Data Types: double | single

IntegratedWaterVaporContent — Integrated water vapor content

scalar

Integrated water vapor content exceeded for the percentage of GasAnnualExceedance in an average year, from the surface of the Earth at the specified location, specified as the comma-separated pair consisting of IntegratedWaterVaporContent and a scalar. Units are in kg/m² or mm. You can derive the value from local measurement or obtain from the integrated digital maps provided in Recommendation ITU-R P.2145.

Data Types: double | single

IntegratedCloudContent — Integrated cloud liquid water content

scalar

Integrated cloud liquid water content exceeded for the percentage of CloudAnnualExceedance in an average year, from the surface of the Earth at the specified location, specified as the comma-separated pair consisting of TotalColumnarContent and a scalar. Units are in kg/m² or mm. You can derive the value from local measurement or obtain from the integrated digital maps provided in Recommendation ITU-R P.840.

For release prior to R2026, see the Version History note Argument IntegratedCloudContent replaces TotalColumnarContent.

Data Types: double | single

RainRate — Point rainfall rate

nonnegative scalar

Point rainfall rate at the location for 0.01% of an average year, specified as the comma-separated pair consisting of RainRate and a nonnegative scalar. Units are in mm/hr. If the local data is not available as an input, the function uses the digital maps provided in ITU-R P.837, Annex 1 [5] to obtain the value of the point rainfall rate.

Data Types: double | single

WetSurfaceRefractivity — Median value of wet term of surface refractivity

nonnegative scalar

Median value of the wet term of the surface refractivity, specified as the comma-separated pair consisting of WetSurfaceRefractivity and a nonnegative scalar. If the local data is not available as an input, the function uses the digital maps provided in ITU-R P.453 section 2.2, Annex 1 [6] to obtain the value of the wet surface refractivity.

Data Types: double | single

MeanRadiatingTemperature — Atmospheric mean radiating temperature

nonnegative scalar

Atmospheric mean radiating temperature in kelvin, specified as the comma-separated pair consisting of MeanRadiatingTemperature and a nonnegative scalar. If the local data is not available as an input, the function uses an atmospheric mean radiating temperature of 275 K in the computation.

Data Types: double | single

Output Arguments

pl — Earth-space propagation losses information

structure

Earth-space propagation losses information, returned as a structure containing these fields.

Fields	Description
At	Total atmospheric attenuation (in dB)
Ag	Gaseous attenuation (in dB)
Ac	Cloud and fog attenuation (in dB)
Ar	Rain attenuation (in dB)
As	Attenuation due to tropospheric scintillation (in dB)

xpd — Cross-polarization discrimination

scalar

Cross-polarization discrimination in (dB) not exceeded for the percentage of the RainAnnualExceedance, returned as a scalar.

tsky — Sky noise temperature

nonnegative scalar

Sky noise temperature (in kelvin) at the ground station antenna, returned as a nonnegative scalar.

Tips

For MATLAB version R2025b or earlier, the p618PropagationLosses object uses ITU-R P.618-13 for its calculations instead of ITU-R P.618-14.

Use this code to download and unzip the MAT files containing digital maps from the ITU-R P.618-13 documents. The code also adds the extracted files to your MATLAB path.

maps = exist('maps.mat','file');
p836 = exist('p836.mat','file');
p837 = exist('p837.mat','file');
p840 = exist('p840.mat','file');
matFiles = [maps p836 p837 p840];
if ~all(matFiles)
    if ~exist('ITURDigitalMaps.tar.gz','file')
        url = 'https://www.mathworks.com/supportfiles/spc/P618/ITURDigitalMaps.tar.gz';
        websave('ITURDigitalMaps.tar.gz',url);
        untar('ITURDigitalMaps.tar.gz');
    else
        untar('ITURDigitalMaps.tar.gz');
    end
    addpath(cd);
end

To run the examples, replace the corresponding code fragment that downloads and unzips the latest digital maps from ITU-R P.618-14 in each example with this to ensure compatibility with ITU-R P.618-13.

References

[1] International Telecommunication Union, ITU-R Recommendation P.618 (08/2023).

[2] International Telecommunication Union, ITU-R Recommendation P.676 (08/2022).

[3] International Telecommunication Union, ITU-R Recommendation P.1511 (08/2024).

[4] International Telecommunication Union, ITU-R Recommendation P.840 (08/2023).

[5] International Telecommunication Union, ITU-R Recommendation P.837 (06/2017).

[6] International Telecommunication Union, ITU-R Recommendation P.453 (08/2019).

[7] International Telecommunication Union, ITU-R Recommendation P.839 (09/2013).

[8] International Telecommunication Union, ITU-R Recommendation P.838 (03/2005).

[9] International Telecommunication Union, ITU-R Recommendation P.2145 (08/2022).

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

Supports only MEX code generation.

Version History

Introduced in R2021a

R2026a: Support for ITU-R P.618-14

The p618PropagationLosses feature now uses ITU-R P.618-14 for its calculations.

R2026a: Argument IntegratedCloudContent replaces TotalColumnarContent

The name-value argument IntegratedCloudContent replaces TotalColumnarContent to align with the terminology used in ITU-R P.840 [4].