# 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

example

````[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 recommendation [1]. `p618cfg` specifies the P.618 configuration parameters.This function requires MAT-files with digital maps from International Telecommunication Union (ITU) documents. If they are not available on the path, download and uncompress the data files from https://www.mathworks.com/supportfiles/spc/P618/ITURDigitalMaps.tar.gz to a location on the MATLAB path.```

example

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

## Examples

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This example requires MAT-files with digital maps from ITU documents. If they are not available on the path, execute the following commands to download and unzip the MAT-files.

```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```

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: 0.2269 Ac: 0.4552 Ar: 6.7981 As: 0.2633 At: 15.6091 ```
```xpd = 32.8876 ```
```tsky = 267.4689 ```

This example requires MAT-files with digital maps from ITU documents. If they are not available on the path, execute the following commands to download and untar the MAT-files.

```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```

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$\frac{\mathit{g}}{{\mathit{m}}^{3}}$, the total columnar content of the cloud liquid water as 1.4 $\frac{\mathrm{kg}}{{\mathit{m}}^{2}}$, 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: 0.8649 Ac: 1.0987 Ar: 0.8907 As: 0.1372 At: 2.8590 ```

This example requires MAT-files with digital maps from ITU documents. If they are not available on the path, execute the following commands to download and unzip the MAT-files.

```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```

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: 0.7996 Ac: 0.8793 Ar: 0.0177 As: 0.3187 At: 1.7514 ```

## Input Arguments

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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.

Height of the earth station above the mean sea level in km, specified as the comma-separated pair consisting of '`StationHeight`' and a nonnegative scalar. The maximum supported value is 100. 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 of the earth surface in kelvin, specified as the comma-separated pair consisting of '`Temperature`' and a nonnegative scalar. If the local data is not available as an input, the function uses the map of the mean annual surface temperature provided in ITU-R P.1510 section 1, Annex 1 [4] to obtain the temperature value.

Data Types: `double` | `single`

Dry air pressure at the earth surface in hPa, specified as the comma-separated pair consisting of '`Pressure`' and a nonnegative scalar. If the local data is not available as an input, the function uses the mean annual global reference atmosphere provided in ITU-R P.835 section 1.1, Annex 1 [5] to obtain the air pressure value.

Data Types: `double` | `single`

Surface water vapor density in g/m3, specified as the comma-separated pair consisting of '`WaterVaporDensity`' 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.836 section 1, Annex 1 [6] to estimate the value of the water vapor density.

Data Types: `double` | `single`

Integrated water vapor content exceeded for the percentage of GasAnnualExceedance in an average year, specified as the comma-separated pair consisting of '`IntegratedWaterVaporContent`' and a positive scalar. Units are in kg/m2 or mm. If the local data is not available as an input, the function uses the digital maps provided in ITU-R P.836 section 1, Annex 2 [6] to obtain the value of the integrated water vapor content.

Data Types: `double` | `single`

Total columnar content of the cloud liquid water exceeded for the percentage of CloudAnnualExceedance in an average year, specified as the comma-separated pair consisting of '`TotalColumnarContent`' and a nonnegative scalar. Units are in kg/m2 or mm. If the local data is not available as an input, the function uses the digital maps provided in ITU-R P.840 section 3.1, Annex 1 [7] to obtain the value of the total columnar content.

Data Types: `double` | `single`

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 [8] to obtain the value of the point rainfall rate.

Data Types: `double` | `single`

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 [9] to obtain the value of the wet surface refractivity.

Data Types: `double` | `single`

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

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

FieldsDescription
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)

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

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

## References

[1] International Telecommunication Union, ITU-R Recommendation P.618 (12/2017).

[2] International Telecommunication Union, ITU-R Recommendation P.676 (08/2019).

[3] International Telecommunication Union, ITU-R Recommendation P.1511 (08/2019).

[4] International Telecommunication Union, ITU-R Recommendation P.1510 (06/2017).

[5] International Telecommunication Union, ITU-R Recommendation P.835 (12/2017).

[6] International Telecommunication Union, ITU-R Recommendation P.836 (12/2017).

[7] International Telecommunication Union, ITU-R Recommendation P.840 (08/2019).

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

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

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

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

## Version History

Introduced in R2021a