# Documentation

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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) ```