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radarpropfactor

One-way radar propagation factor

Description

F = radarpropfactor(R,freq,ANHT) calculates the one-way propagation factor assuming a surface target and a sea state of 0. The calculation estimates the complex relative permittivity (dielectric constant) of the reflecting surface using a sea water model described in [1] that is valid from 100 MHz to 10 GHz. The target height is assumed to be the height of significant clutter sources above the average surface height. Specifically, the target height is calculated as 3 times the standard deviation of the surface height. Assuming the paths are the same, the two-way propagation factor is 2F.

F = radarpropfactor(___,TGTHT) calculates the target propagation factor assuming a target height of TGTHT.

example

F = radarpropfactor(___,Name,Value) allows you to specify additional input parameters as Name-Value arguments. You can specify additional name-value pair arguments in any order as Name1,Value1,...,NameN,ValueN. This syntax can use any of the input arguments in the previous syntax.

radarpropfactor(___) plots the one-way propagation factor in dB versus range in km. Default range units are km.

Examples

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Plot the propagation factor for a 3 GHz S-band radar assuming an antenna height of 10 m and a target height of 1 km. Assume that the surface has a height standard deviation of 1 m, and the surface slope is 0.05 degrees.

R     = (30:0.5:180)*1e3; % Range (m)
freq  = 3e9;              % Frequency (Hz)
anht  = 10;               % Radar height (m)
tgtht = 1e3;              % Target height (m)
hgtsd = 1;                % Height standard deviation (m)
beta0 = 0.05;             % Surface slope (deg)

radarpropfactor(R,freq,anht,tgtht,...
    'SurfaceHeightStandardDeviation',hgtsd,...
    'SurfaceSlope',beta0)

Figure Propagation Factor contains an axes. The axes with title Propagation Factor {\itF} contains an object of type line.

Input Arguments

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Free space range, specified as a scalar or an M-length vector. Units are in meters.

Example: 0.5

Data Types: single | double

Radar frequency in hertz, specified as a positive real scalar or a vector.

Data Types: double

Antenna height as referenced from ground level, specified as a positive scalar. Units are in meters.

Data Types: double

Target height as referenced from ground level, specified as a positive scalar. Units are in meters.

Data Types: double

Name-Value Pair Arguments

Specify optional comma-separated pairs of Name,Value arguments. Name is 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 Name1,Value1,...,NameN,ValueN.

Example: 'SurfaceHeightStandardDeviation',hgtsd,'SurfaceSlope',beta0

Polarization of the transmitted wave, specified as 'H' or 'V'. 'H' indicates horizontal polarization and 'V' indicates vertical polarization.

Complex relative permittivity (dielectric constant) of the reflecting surface, specified as a complex scalar. The default value of dielectric constant depends on the value of the freq argument. The function uses a sea water model in [1] that is valid up to 10 GHz.

Data Types: single | double
Complex Number Support: Yes

Standard deviation of the surface height in meters, specified as positive scalar. The default value of 0.01 m indicates a sea state of 0. Units are in meters.

Data Types: single | double

Surface slope, specified as a nonnegative scalar. This value is expected to be 1.4 times the RMS surface slope. Given the condition that 2*GRAZ/BETA0 < 1, where GRAZ is the grazing angle of the geometry specified in degrees, the effective surface height standard deviation in meters is calculated as

Effective HGTSD = HGTSD*(2*GRAZ/BETA0)^(0.2)

This calculation better accounts for shadowing. Otherwise, the effective height standard deviation is equal to HGTSD. BETA0 defaults to the surface slope value output by the searoughness function for a sea state of 0. Units are in degrees.

Data Types: single | double

Surface vegetation type, specified as 'Trees', 'Weeds', and 'Brush' are assumed to be dense vegetation. 'Grass' is assumed to be thin grass. Use this argument when using the function on surfaces different from the sea.

Half-power elevation beamwidth, specified as a scalar between 0° and 90°. The elevation beamwidth is used in the calculation of a sinc antenna pattern. The default antenna pattern is symmetrical with respect to the beam maximum and is of the form sin(u)/u. The parameter u is given by u = k*sin(theta), where theta is the elevation angle in radians and k is given by k = 1.39157/sin(ELBW/2). Units are in degrees.

Data Types: double

Antenna elevation pattern, specified as an M-length vector. This is an alternative to specifying the elevation beamwidth. Both 'AntennaPattern' and 'PatternAngle' arguments must be vectors of the same size. If both an antenna pattern and elevation beamwidth are provided, the function uses the antenna pattern and ignores the elevation beamwidth value. Defaults to a sinc antenna pattern.

Data Types: double

Antenna pattern angle, specified as an M-length vector corresponding to the 'AntennaPattern' argument. In general, to properly compute the coverage, the pattern should be specified from -90° to 90°. Units are in degrees.

Data Types: double

Tilt angle of the antenna with respect to the surface, specified as a scalar between -90° and 90°. Units are in degrees.

Data Types: double

Effective Earth radius, specified as a positive scalar. The default value calculates the effective Earth radius using a refraction gradient of -39e-9, which results in approximately 4/3 of the real earth radius. Units are in meters.

Data Types: double

Refractive index at the surface, specified as a nonnegative scalar. Defaults to approximately 1.000318, which is the output of the refractiveidx function at an altitude of 0 meters.

Data Types: double

Output Arguments

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The one-way propagation factor, returned as a scalar or M-length column vector. Units are in decibels.

References

[1] Blake, L.V. "Machine Plotting of Radar Vertical-Plane Coverage Diagrams." Naval Research Laboratory, 1970 (NRL Report 7098).

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Introduced in R2021a