Slant-path loss due to atmosphere gaseous absorption
calculates the path loss due to tropospheric refraction using the International
Telecommunication Union (ITU) standard atmospheric model known as the mean annual global
reference atmosphere (MAGRA), which approximates the U.S. Standard Atmosphere 1976 with
insignificant relative error.
Lgas = tropopl(
calculates the corresponding lens loss. The variation in refractivity versus altitude makes
the atmosphere act like a lens with loss independent of frequency. Rays leaving an antenna
are refracted in the troposphere and the energy radiated within some angular extent is
distributed over a slightly greater angular sector, thereby reducing the energy density
relative to propagation in a vacuum.
Llens] = tropopl(___)
Plot Attenuation Versus Range for 100 GHz Radar Frequency
Calculate the attenuation versus range for a frequency of
100 GHz with an elevation of
5 degrees using the mid-latitude, winter atmospheric model.
R = (10:200)*1e3; % m f = 100e9; % Hz ht = 0; % m el = 5; % deg Lgas = tropopl(R,f,ht,el,'LatitudeModel','Mid','Season','Winter');
Plot the results.
semilogy(R.*1e-3,Lgas); xlabel('Range (km)'); ylabel('Attenuation (dB)'); title('Attenuation for Mid-Latitude, Winter Atmosphere');
R — Slant range
positive scalar | M-length vector
Slant range, specified as a positive scalar or an M-length column vector. Units are in meters.
F — Radar frequency
positive scalar | N-length vector
Radar frequency, specified as a positive real scalar or N-length row vector. Units are in Hz.
H — Altitude of radar platform
Mean sea level (MSL) altitude of the radar platform, specified as a positive scalar
100 km. Values outside the specified
range result in
NaN output. Units are in meters.
EL — Elevation angle
Elevation angle of the propagation path, specified as a scalar. Units are in degrees.
Specify optional pairs of arguments as
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.
WaterVaporDensity — Standard ground-level water vapor density
7.5 (default) | positive scalar
Standard ground-level water vapor density, specified as a positive scalar in
g/m3. Applicable only for the
default standard model (MAGRA). Defaults to 7.5
ScaleHeight — Scale height above mean sea level
2e3 (default) | positive scalar
Altitude above mean sea level (MSL), specified as a positive scalar in meters.
Applicable only for the default standard model (MAGRA). Defaults to
2e3 meters. For a dry atmospheric conditions, set scale height to
LatitudeModel — Reference latitude model
'Standard' (default) |
Reference latitude model, specified as one of these.
This model is the mean annual global reference atmosphere (MAGRA) that reflects the mean annual temperature and pressure averaged across the world.
This model is for low latitudes less than
This model is for mid latitudes between
This model is for high latitudes greater than
Season — Season
'Summer' (default) |
Season for the
models, specified as
models ignore this input. Defaults to
AtmosphereMeasurements — Custom atmosphere measurements
Custom atmospheric measurements for the calculation of the refractive index,
specified as an N-by-
4 matrix, where
N corresponds to the number of altitude measurements.
N must be greater than or equal to 2. The first column is the
atmospheric temperature in kelvins, the second column is the atmospheric pressure in
hPa, the third column is the water vapor density in g/m3,
and the fourth column is the MSL altitude of the measurements in meters. When you use
a custom model, all other name-value arguments are ignored and the output refractive
index is applicable for the input height.
The model used by
lenspl assumes geometrical optics
conditions, as a result anomalous propagation like ducting and sub-refraction cannot
be present in provided measurements. If atmospheric measurements evidencing ducting
and sub-refraction are provided, this function throws an error.
Pressure and Temperature Units
One hPa equals 100 Pa and K = C + 273.15. Use caution when combining the use of these three functions.
The atmosphere is a used in tropopl is a layered model with temperature, pressure, and water vapor density dependent on altitude.