# Documentation

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# comm.PAMModulator System object

Modulate using M-ary PAM method

## Description

The PAMModulator object modulates using M-ary pulse amplitude modulation. The output is a baseband representation of the modulated signal. The M-ary number parameter, M, represents the number of points in the signal constellation and requires an even integer.

To modulate a signal using M-ary pulse amplitude modulation:

1. Define and set up your PAM modulator object. See Construction.

2. Call step to modulate the signal according to the properties of comm.PAMModulator. The behavior of step is specific to each object in the toolbox.

### Note

Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

## Construction

H = comm.PAMModulator creates a modulator System object, H. This object modulates the input signal using the M-ary pulse amplitude modulation (M-PAM) method.

H = comm.PAMModulator(Name,Value) creates an M-PAM modulator object, H, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

H = comm.PAMModulator(M,Name,Value) creates an M-PAM modulator object, H. This object has the ModulationOrder property set to M and the other specified properties set to the specified values.

## Properties

 ModulationOrder Number of points in signal constellation Specify the number of points in the signal constellation as a positive, integer scalar value. The default is 4. When you set the BitInput property to false, ModulationOrder must be even. When you set the BitInput property to true, ModulationOrder must be an integer power of two. BitInput Assume bit inputs Specify whether the input is in bits or integers. The default is false. When you set this property to true, the step method input requires a column vector of bit values whose length is an integer multiple of log2(ModulationOrder). This vector contains bit representations of integers between 0 and ModulationOrder–1. When you set this property to false, the step method input must be a column vector of integer symbol values between 0 and ModulationOrder–1. SymbolMapping Constellation encoding Specify how the object maps an integer or group of log2(ModulationOrder) input bits to the corresponding symbol as one of Binary | Gray. The default is Gray. When you set this property to Gray, the object uses a Gray-encoded signal constellation. When you set this property to Binary, the input integer m, between $0\le m\le$ModulationOrder-1) maps to the complex value 2m– ModulationOrder + 1. NormalizationMethod Constellation normalization method Specify the method used to normalize the signal constellation as one of Minimum distance between symbols | Average power | Peak power. The default is Minimum distance between symbols. MinimumDistance Minimum distance between symbols Specify the distance between two nearest constellation points as a positive, real, numeric scalar value. The default is 2. This property applies when you set the NormalizationMethod property to Minimum distance between symbols. AveragePower Average power of constellation Specify the average power of the symbols in the constellation as a positive, real, numeric scalar value. The default is 1. This property applies when you set the NormalizationMethod property to Average power. PeakPower Peak power of constellation Specify the maximum power of the symbols in the constellation as a positive, real, numeric scalar value. The default is 1. This property applies when you set the NormalizationMethod property to Peak power. OutputDataType Data type of output Specify the output data type as one of double | single | Custom. The default is double.

## Methods

 constellation Calculate or plot ideal signal constellation step Modulate using M-ary PAM method
Common to All System Objects
clone

Create System object with same property values

getNumInputs

Expected number of inputs to a System object

getNumOutputs

Expected number of outputs of a System object

isLocked

Check locked states of a System object (logical)

release

Allow System object property value changes

## Examples

Modulate data using 16-PAM modulation, and visualize the data in a scatter plot.

% Create binary data for 100, 4-bit symbols
data = randi([0 1],400,1);
% Create a 16-PAM modulator System object with bits as inputs and
% Gray-coded signal constellation
hModulator = comm.PAMModulator(16,'BitInput',true);
% Modulate and plot the data
modData = step(hModulator, data);
constellation(hModulator)

## Algorithms

This object implements the algorithm, inputs, and outputs described on the M-PAM Modulator Baseband block reference page. The object properties correspond to the block parameters.