comm.PAMModulator System object

Package: comm

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.

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 0mModulationOrder-1) maps to the complex value 2mModulationOrder + 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.

 Fixed-Point Properties

Methods

cloneCreate PAM modulator object with same property values
constellationCalculate or plot ideal signal constellation
getNumInputsNumber of expected inputs to step method
getNumOutputsNumber of outputs from step method
isLockedLocked status for input attributes and nontunable properties
releaseAllow property value and input characteristics changes
stepModulate using M-ary PAM method

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.

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