Engee documentation

lenspl

Calculation of losses caused by the tropospheric focusing effect.

Library

EngeePhased

Syntax

Function call

  • L = lenspl(R,platformHeight,el) — Calculates unilateral losses due to the tropospheric focusing effect using the International Telecommunication Union (ITU) standard atmospheric model known as the Mean Annual Global Reference Atmosphere (MAGRA), which approximates the 1976 standard atmosphere of the United States with a slight relative error. Changing the refractive index as a function of altitude causes the atmosphere to act as a lens, the loss of which is independent of frequency. The rays coming from the antenna are refracted in the troposphere, and the energy radiated within a certain angular range is distributed over a slightly larger angular sector, thereby reducing the energy density compared to propagation in a vacuum.

  • L = lenspl(___,Name=Value) — sets parameters using one or more arguments of the type «name-value» in addition to the input arguments of the previous syntax.

Arguments

Input arguments

# platformHeight — height of the radar installation

+ scalar

Details

The height of the radar installation above mean sea level in meters, set as a scalar of 0 before 100 Values outside the specified range lead to the output NaN.

Типы данных

Float32, Float64

# el — elevation angle

+ scalar | vector

Details

The elevation angle of the propagation path in degrees, set as a scalar or a real vector of length .

Типы данных

Float32, Float64

# R — oblique range

+ scalar | vector

Details

The oblique range in meters, set as a positive scalar or a real length vector .

Типы данных

Float32, Float64

Input arguments «name-value»

Specify optional argument pairs in the format Name = Value, where Name — the name of the argument, and Value — the appropriate value. Type arguments «name-value» they should be placed after the other arguments, but the order of the pairs does not matter.

# WaterVaporDensity — standard absolute humidity at ground level

+ 7.5 (by default) | scalar

Details

The standard absolute humidity at ground level in g/m 3, set as a positive scalar. Applicable only for the default standard model (MAGRA).

Типы данных

Float32, Float64

# ScaleHeight — height above sea level

+ 2.0e3 (by default) | scalar

Details

The height above mean sea level in meters, set as a positive scalar. Applicable only for the default standard model (MAGRA). In a dry atmosphere, set this argument to 6.0e3 m.

Типы данных

Float32, Float64

# LatitudeModel — Latitude reference model

+ "Standard" (by default) | "Low" | "Mid" | "High"

Details

The reference model of latitude, set as one of the following values:

  • "Standard" — The model represents the Standard Global Atmosphere (MAGRA), characterized by annual averages of temperature and pressure around the globe.

  • "Low" — the model is designed for low latitudes less than 22 degrees, where seasonal fluctuations are insignificant.

  • "Mid" — the model is designed for mid-latitudes from 22 before 45 degrees with seasonal profiles for values "Summer" and "Winter", set using the argument Season.

  • "High" — the model is designed for higher latitudes than 45 degrees with seasonal profiles for values "Summer" and "Winter", set using the argument Season.

# Season — seasonal profile

+ "Summer" (by default) | "Winter"

Details

Seasonal profile for latitude models "Mid" and "High", set as "Summer" or "Winter". Other latitude models ignore this argument.

# Atmospheremeasuries — Custom atmospheric measurements

+ the matrix

Details

Custom atmospheric measurements for calculating the refractive index, specified as a matrix size on , where — the number of height measurements. Meaning must be greater than or equal to 2. The first column of the matrix is the atmospheric temperature in kelvin, the second column is atmospheric pressure in gPa, the third column is absolute humidity in g/m3, and the fourth column is the measurement altitude above mean sea level in meters. When using a custom model, all other arguments are of the type «name-value» are ignored, and the output refractive index is applied to the input height.

The model used by the function lenspl, is based on the assumptions of geometric optics, so waveguide propagation and sub-refraction should not be present in the provided measurements. If atmospheric measurements are provided that demonstrate waveguide propagation and subrefraction, this function will return an error.
Типы данных

Float32, Float64

Output arguments

# L — lens loss

+ scalar | vector

Details

Unilateral lens losses in dB, returned as a scalar or a real length vector .

Examples

Graph of the two-way lens loss curve

Details

Let’s calculate the curve of two-way lens losses for a radar installation at sea level at an elevation angle 0.03 degrees at an inclined range from 100 before 5000 km.

import EngeePhased.Functions: lenspl

h = 0.0                   # m
el = 0.03                 # deg
R = (100:5000) .* 1e3     # m
L = 2 * lenspl(R, h, el)  # Factor of 2 for two-way propagation

Let’s plot the dependence of losses in the lens on the inclined range.

plot(R .* 1e-3, L, xlabel = "Range (km)",
                   ylabel = "Loss (dB)",
                   title = "Two-Way Lens Loss")

lenspl