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Plot Signal Constellations

Create 16-PSK Constellation Diagram

This example shows how to plot a PSK constellation having 16 points.

Set the parameters for 16-PSK modulation with no phase offset and binary symbol mapping.

M = 16;             % Modulation alphabet size
phOffset = 0;       % Phase offset
symMap = 'binary';  % Symbol mapping (either 'binary' or 'gray')

Construct the modulator object.

pskModulator = comm.PSKModulator(M,phOffset,'SymbolMapping',symMap);

Plot the constellation.

constellation(pskModulator)

Create 32-QAM Constellation Diagram

This example shows how to plot a QAM constellation having 32 points.

Construct the modulator object using name-value pairs to set the properties.

qamModulator = comm.RectangularQAMModulator('ModulationOrder',32, ...
    'SymbolMapping','binary');

Plot the constellation.

constellation(qamModulator)

Create 8-QAM Gray Coded Constellation Diagram

This example shows how to plot a Gray-coded 8-QAM constellation.

Construct the modulator object using a name-value pair to set the properties. Note that Gray coding is the default symbol mapping for the comm.RectangularQAMModulator System object.

qamModulator = comm.RectangularQAMModulator('ModulationOrder',8);

Plot the constellation.

constellation(qamModulator)

Plot a Triangular Constellation for QAM

This example shows how to plot a customized QAM reference constellation.

Describe the constellation.

inphase = [1/2 -1/2 1 0 3/2 -3/2 1 -1];
quadr = [1 1 0 2 1 1 2 2];
inphase = [inphase; -inphase];
inphase = inphase(:);
quadr = [quadr; -quadr];
quadr = quadr(:);
refConst = inphase + 1i*quadr;

Construct a constellation diagram System object using name-value pairs to specify the title, the axes limits, the reference marker type, and the reference marker color.

constDiagram = comm.ConstellationDiagram('Title','Customized Constellation for QAM', ...
    'XLimits',[-3 3],'YLimits',[-3 3], ...
    'ReferenceConstellation',refConst, ...
    'ReferenceMarker','*','ReferenceColor',[0 1 0]);

Plot the customized constellation.

constDiagram(refConst)

See Also

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