SurfaceReflectionCoefficient

Reflection coefficient model for land and sea surfaces

Since R2024a

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    Description

    SurfaceReflectionCoefficient defines a frequency and grazing angle dependent reflection coefficient model for a LandSurface or SeaSurface object belonging to a radar scenario in which the EnableMultipath property of the SurfaceManager is set to true. The reflection coefficient for multipath calculations can be computed using the reflectionCoefficient object function for a horizontally or vertically polarized antenna.

    Creation

    Syntax

    MDL = radar.scenario.SurfaceReflectionCoefficient
    MDL = SurfaceReflectionCoefficient(Name=Value)

    Description

    MDL = radar.scenario.SurfaceReflectionCoefficient creates a SurfaceReflectionCoefficient object containing a reflection coefficient model for a land or sea surface belonging to a radar scenario.

    example

    MDL = SurfaceReflectionCoefficient(Name=Value) creates a SurfaceReflectionCoefficient object containing a reflection coefficient model for a land or sea surface and sets properties using one or more name-value pairs, where Name specifies the property name and Value sets the corresponding property value. The PermittivityModel, VegetationFactor, HeightStandardDeviation, and Slope property can be defined

    Properties

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    Complex relative permittivity (dielectric constant) of the reflecting surface, specified as a model or a complex scalar. The earthSurfacePermittivity function is the default model. For a LandSurface, the earthSurfacePermittivity model of a dry sandy loam is used. For a SeaSurface, the earthSurfacePermittivity model of relative permittivity and conductivity for sea water is used. If a function handle is used it must accept the operating frequency in hertz of the radar as its single input argument and return either the complex relative permittivity as its single output argument or the real relative permittivity and the conductivity as two separate output arguments. The complex relative permittivity is used by the reflectionCoefficient object function to calculate the Fresnel reflection coefficient.

    Data Types: double
    Complex Number Support: Yes

    Vegetation factor specified either as a vegetation type or a nonnegative scalar, with a default value of None. A vegetation factor of 1, or None, means that all of the energy is reflected (no absorption) by the surface and a value of 0 corresponds to total absorption by the surface, or complete vegetation cover [1]. Dense vegetation is assumed for Trees, Weeds, or Brush and sparse vegetation is assumed for Grass.

    Data Types: double | char | string
    Complex Number Support: Yes

    Standard deviation of the surface height, specified as a nonnegative scalar. By default, for a LandSurface object, HeightStandardDeviation corresponds to Barton's model for flatland from Land Models and Land Types. For a SeaSurface object, this property is set to the standard deviation of the surface height returned by the searoughness function for a Blake's model sea state of 0. A value of 0 indicates a smooth surface. Units are in meters.

    Data Types: double

    Surface slope, specified as a nonnegative scalar in degrees. By default, for a LandSurface object, Slope is set to the slope for Barton's model for flatland from Land Models and Land Types. For a SeaSurface object, the property is set to the slope (beta0) returned by the searoughness function for a Blake's model sea state of 0.

    This value is expected to be 1.4 times the RMS surface slope. Given the condition that

    2 × GRAZ/β0 < 1,

    where GRAZ is the grazing angle of the geometry for multipath reflection is specified in degrees and β0 is the surface slope, the effective height standard deviation in meters is calculated as

    Effective HGTSD = HGTSD × (2 × GRAZ/β0)1/5.

    This calculation better accounts for shadowing. Otherwise, the effective height standard deviation is equal to HGTSD. GRAZ is set in the reflectionCoefficient object function that can be called on the SurfaceReflectionCoefficient object.

    Data Types: double

    Object Functions

    reflectionCoefficientReturns the reflection coefficient

    Examples

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    Open Live Script

    This example shows how to modify the SurfaceReflectionCoefficient model that is used for multipath calculations.

    % create a radar scenario
% set IsEarthCentered to false models a flat Earth
scene = radarScenario(UpdateRate=0,IsEarthCentered=false);  

% enable multipath modeling
scene.SurfaceManager.EnableMultipath = true; 

% create a land surface
srf = landSurface(scene);

% view default reflection coefficient model
reflc_model = srf.ReflectionCoefficient
    reflc_model = 
  SurfaceReflectionCoefficient with properties:

          PermittivityModel: @(freq)earthSurfacePermittivity("soil",freq,temp,pctSand,pctClay,ps,mv,pb)
           VegetationFactor: "None"
    HeightStandardDeviation: 1
                      Slope: 1.1459


    % modify default reflection coefficient model
reflc_model.HeightStandardDeviation = 2;
reflc_model.VegetationFactor = "Grass"
    reflc_model = 
  SurfaceReflectionCoefficient with properties:

          PermittivityModel: @(freq)earthSurfacePermittivity("soil",freq,temp,pctSand,pctClay,ps,mv,pb)
           VegetationFactor: "Grass"
    HeightStandardDeviation: 2
                      Slope: 1.1459

    References

    [1] Barton, David Knox. Radar Equations for Modern Radar. Artech House, 2013.

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

    Version History

    Introduced in R2024a

    See Also

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