CustomSurface

Custom surface with complex scattering belonging to a radar scenario

Since R2024a

Description

CustomSurface defines a custom surface object belonging to a radar scenario, radarScenario. The object describes the extent and complex scattering response of the surface. You can use the CustomSurface object to update polarization scattering matrices, determine surface heights, and test for occlusion. CustomSurface objects are compatible with I/Q sensors generated by radarTransceiver and require that the scenario sensor, surface, and targets are polarized. Scattering matrices are specific to a single frequency and viewing geometry and are therefore relevant to a single sensor attached to the radarScenario. Effects due to occlusion should be modeled within the surface scattering matrix.

Creation

Create CustomSurface objects using the customSurface object function of the radarScenario object.

Properties

Boundary — Bounding rectangle of surface (degrees)

[-60 60; -60 60] (default) | finite 2-by-2 matrix

Extent of the rectangular custom surface, specified as a 2-by-2 finite matrix in units of degrees. The bounding rectangle is defined by two 2-dimensional points in either Cartesian or geodetic scenario coordinates. When the IsEarthCentered property of the radarScenario object is specified as:

• false — Scenario coordinates are Cartesian. Specify the bounding rectangle as [minX, maxX, minY maxY]. minX and maxX are the minimum and maximum values in the x-direction of the reference frame, where minX < maxX. minY and maxY are the minimum and maximum values in the y-direction of the reference frame, where minY < maxY.

• true — Scenario coordinates are geodetic. Specify the bounding rectangle as [startLat, endLat, startLon endLon]. startLat and endLat are the minimum and maximum latitudes of the geodetic frames, where startLat and endLat must lie in the interval [–90,90] and startLat < endLat. startLon and endLon are the minimum and maximum longitudes of the geodetic frame and must lie in the interval [–180,180]. If endLon < startLon, the object wraps endLon to startLon + 360°. Units are in degrees.

The resolution of surface patches within Boundary is given by resX = lengthX / numX for the x-dimension. Similarly, the resolution for the y-dimension is resY = lengthY / numY. lengthX and lengthY are calculated as the differences of the Boundary coordinates in the x- and y- dimensions, respectively. The number of surface patches within the boundary is determined by the size of the scattering matrix component Shh. For the x-dimension, numX = size(Shh,1) and for the y-dimension, numY = size(Shh,2). Note, the clutterGenerator Resolution property for the radarScenario should match the resolution of the custom surface to prevent resampling of the surface. For example, if you have a surface that is 500-by-1 km in Cartesian space with a clutterGenerator Resolution set to 50 m, the Boundary could be specified as [–200 300; 100 1100]. For this case, the polarization scattering matrix components (Shh, Svv, Shv, and Svh) should be of size 20-by-10 m because numX = (maxX – minX) / resX, and numY = (maxY – minY) / resY.

Data Types: double

CrossPolarization — Polarization scattering matrix type

"full" (default) | "symmetric"

Specify the polarization scattering matrix as either full or symmetric. If CrossPolarization is full, the polarization matrix components Shh, Svv, Shv, and Svh must all be specified. If CrossPolarization is set to symmetric, reciprocity is assumed (monostatic geometry), and the cross-polarization terms are considered to be equivalent (Shv = Svh). Therefore, Shv is automatically set to the same value as Svh and cannot be modified.

Data Types: char | string

Shh — Polarization scattering matrix co-polarized HH component

3-by-3-by-2 matrix of ones (default) | M-by-N-by-P matrix

Specify the complex-valued polarization scattering matrix co-polarized HH component, where HH represents horizontal transmission and horizontal reception, as an M-by-N-by-P matrix. M indicates the number of components in the x-direction, N indicates the number of components in the y-direction, and P corresponds to the number of elements in the Frequency vector. The matrix is bounded in space by the Boundary property limits.

Data Types: double
Complex Number Support: Yes

Svv — Polarization scattering matrix co-polarized VV component

3-by-3-by-2 matrix of ones (default) | M-by-N-by-P matrix

Specify the complex-valued polarization scattering matrix co-polarized VV component, where VV represents vertical transmission and vertical reception, as an M-by-N-by-P matrix. M indicates the number of components in the x-direction, N indicates the number of components in the y-direction, and P corresponds to the number of elements in the Frequency vector. The matrix is bounded in space by the Boundary property limits.

Data Types: double
Complex Number Support: Yes

Shv — Polarization scattering matrix cross-polarized HV component

3-by-3-by-2 matrix of ones (default) | M-by-N-by-P matrix

Specify the complex-valued polarization scattering matrix cross-polarized HV component, where HV represents horizontal transmission and vertical reception, as an M-by-N-by-P matrix. M indicates the number of components in the x-direction, N indicates the number of components in the y-direction, and P corresponds to the number of elements in the Frequency vector. The matrix is bounded in space by the Boundary property limits.

Data Types: double
Complex Number Support: Yes

Svh — Polarization scattering matrix cross-polarized VH component

3-by-3-by-2 matrix of ones (default) | M-by-N-by-P matrix

Specify the complex-valued polarization scattering matrix cross-polarized VH component, where VH represents vertical transmission and horizontal reception, as an M-by-N-by-P matrix. M indicates the number of components in the x-direction, N indicates the number of components in the y-direction, and P corresponds to the number of frequencies in Frequency. The matrix is bounded in space by the Boundary property limits.

Dependencies

To enable this property, set the CrossPolarization property to "full".

Data Types: double
Complex Number Support: Yes

Frequency — Frequencies for the scattering matrix (Hz)

[0 1e20] (default) | length-P row vector

Valid frequencies for the scattering matrix components specified as a length-P row vector, where P is the number of frequencies. Frequency units are in hertz (Hz).

Data Types: double

ReferenceHeight — Surface reference height (m)

0 (default) | scalar

Reference height of surface height data, specified as a scalar. Surface heights are relative to the reference height. Units are in meters.

Data Types: double

Object Functions

updateScatteringMatrix	Update scattering matrices
height	Height of point on surface
occlusion	Test for occlusion of point by a surface

Examples

Create Co-Polarized and Cross-Polarized Custom Surfaces

This example shows how to create a custom surface and update the polarization scattering matrices. Co-polarized and cross-polarized surfaces are compared.

Create Custom Surface

Create a co-polarized custom surface.

% Create a radar scenario
rng('default');
scenario = radarScenario(IsEarthCentered=false);

% Create a co-polarized custom surface
bnds = [-600 570; 0 1.17e3];
Shh  = zeros(40,40,2);
Svv  = ones(40,40,2);
Shv  = zeros(size(Shh));
srf  = customSurface(scenario,Boundary=bnds, ...
     CrossPolarization='symmetric',Shh=Shh,Svv=Svv,Shv=Shv);

Collect I/Q Data

Create a vertically polarized radar I/Q sensor and collect data.

% Create a vertically polarized radar IQ sensor and attach to
% a platform
freq = 500e6;
sweepBW = 5e6;
fs = 2*sweepBW;
wav = phased.LinearFMWaveform(SampleRate=fs, ...
    SweepBandwidth=sweepBW);
rdr = radarTransceiver(Waveform=wav, ...
    MountingAngles=[-90 10 0], ...
    RangeLimits=[0 1.2e3]);
element = phased.ShortDipoleAntennaElement;
ula     = phased.ULA(Element=element);
configureAntennas(rdr,Combined=ula);
rdr.TransmitAntenna.OperatingFrequency = freq;
rdr.ReceiveAntenna.OperatingFrequency = freq;
rdr.Receiver.SampleRate = fs;
rdrplat = platform(scenario,Position=[0 0 10],Sensors=rdr);

% Create clutter generator
cluttergen = clutterGenerator(scenario,rdr,Resolution=30, ...
    RangeLimit=1.2e3);

% Advance scenario and collect IQ
advance(scenario);
iq = receive(scenario);

% Pulse compress
mf = getMatchedFilter(rdr.Waveform);
rngresp = phased.RangeResponse(SampleRate=fs);
[iqPC,rngGrid] = rngresp(iq{1}(:,1),mf);
figure
nexttile
plot(rngGrid,mag2db(abs(iqPC)))
title(['Pulse 1, Element 1' newline 'Co-Polarized Surface'])
xlabel('Range (m)')
ylabel('Magnitude (dB)')
grid on
axis tight
ylim([-80 60])

Update Scattering Matrix Values

Update scattering matrix values for HH and VV components to make the surface cross-polarized and collect I/Q data.

% Update scattering matrix values for HH and VV components.
% Make the surface cross-polarized.
Shh  = ones(40,40,2);
Svv  = zeros(40,40,2);
updateScatteringMatrix(srf,Shh=Shh,Svv=Svv)

% Collect IQ
iq = receive(scenario);
[iqPC,rngGrid] = rngresp(iq{1}(:,1),mf);
nexttile
plot(rngGrid,mag2db(abs(iqPC)))
title(['Pulse 2, Element 1' newline ...
    'Cross-Polarized Surface'])
xlabel('Range (m)')
ylabel('Magnitude (dB)')
grid on
axis tight
ylim([-80 60])

Version History

Introduced in R2024a