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(___)
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
Slant range, specified as a positive scalar or an M-length column vector. Units are in meters.
F— Radar frequency
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 positive scalar. Units are in degrees.
comma-separated pairs of
the argument name and
Value is the corresponding value.
Name must appear inside quotes. You can specify several name and value
pair arguments in any order as
'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
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 for the
models, specified as
models ignore this input. Defaults to
'AtmosphericMeasurements'— Custom atmospheric 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. 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 subrefraction cannot
be present in provided measurements. If atmospheric measurements evidencing ducting
and subrefraction are provided, this function throws an error.