M-PAM Modulator Baseband

Modulate using M-ary pulse amplitude modulation

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Libraries:
Communications Toolbox / Modulation / Digital Baseband Modulation / AM

Description

The M-PAM Modulator Baseband block modulates a signal by using M-ary pulse amplitude modulation. The output is a baseband representation of the modulated signal.

Note

All values of power assume a nominal impedance of 1 ohm.

Examples

Plot M-PAM Constellation in Simulink

The doc_pam_mod model uses the M-PAM Modulator Baseband block to modulate input data. Observe changes in the constellation size and scaling for various normalization methods and modulation orders.

A Random Integer Generator block generates a vector of integers over the range [0, M-1] as input for a modulator that applies M-PAM.

Update mask parameters in the M-PAM Modulator Baseband block. Set the modulation order to 8 and the default minimum distance between symbols normalization method. Click the View Constellation parameter on the M-PAM Modulator Baseband block mask to observe the constellation.

Update the M-PAM Modulator Baseband block mask to set the average power normalization method. Click the View Constellation parameter on the M-PAM Modulator Baseband block mask to observe the change in the constellation scaling.

Update the M-PAM Modulator Baseband block mask to set the peak power normalization method. Click the View Constellation parameter on the M-PAM Modulator Baseband block mask to observe the change in the constellation scaling.

Update the M-PAM Modulator Baseband block mask to set the modulation order to 4. Click the View Constellation parameter on the M-PAM Modulator Baseband block mask to observe the constellation.

Update the M-PAM Modulator Baseband block mask to set the modulation order to 2. Click the View Constellation parameter on the M-PAM Modulator Baseband block mask to observe the constellation.

Extended Examples

ATSC Digital Television

The vestigial sideband modulation with 8 discrete amplitude levels (8-VSB) transmission subsystem of the Advanced Television Systems Committee (ATSC) digital television standard [ 1 ]. The standard describes the characteristics of the U.S. advanced television system that is designed to transmit high-quality video, audio, and ancillary data within a single 6 MHz terrestrial television broadcast channel.

• Open Model

Ports

Input

In — Input signal

scalar | column vector

Input signal, specified as a scalar or column vector. The input data must be binary values or integers in the range [0, (M – 1)], where M is the modulation order as specified by the M-ary number parameter. This port is unnamed on the block.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Output

Out — M-PAM-modulated baseband signal

scalar | column vector

M-PAM-modulated baseband signal, returned as a scalar or column vector. Use the Output data type parameter to specify the output data type. This port is unnamed on the block.

Data Types: single | double | fixed point

Parameters

To edit block parameters interactively, use the Property Inspector. From the Simulink^® Toolstrip, on the Simulation tab, in the Prepare gallery, select Property Inspector.

Main

M-ary number — Modulation order

4 (default) | positive, even integer

Modulation order, specified as a positive, even integer. The modulation order, M, specifies the number of points in the signal constellation. The block scales the signal constellation based on how you set the Normalization method parameter. For more information, see Constellation Size and Scaling.

Input type — Type of input value

Integer (default) | Bit

Type of input value, specified as Integer or Bit. When you set this parameter to Bit, the M-ary number parameter must be 2^K for some positive integer K.

Constellation ordering — Mapping order of symbols

Binary (default) | Gray

Mapping order of the symbols, specified as Gray or Binary. This parameter indicates how the block maps binary words to points of the signal constellation.

• When you set this parameter to Binary, the block uses binary-coded constellation.

• When you set this parameter to Gray, the block uses a Gray-coded constellation.

Normalization method — Scaling method for constellation

Min. distance between symbols (default) | Average Power | Peak Power

Scaling method for the constellation, specified as Min. distance between symbols, Average Power, or Peak Power. For more information, see Constellation Size and Scaling.

Minimum distance — Distance between two nearest constellation points

2 (default) | positive scalar

Distance between the two nearest constellation points, specified as a positive scalar.

Dependencies

This parameter appears when you set Normalization method to Min. distance between symbols.

Average power, referenced to 1 ohm (watts) — Average power

1 (default) | positive scalar

Average power of the symbols in the constellation in watts, specified as a positive scalar. Power values assume a nominal impedance of 1 ohm.

Dependencies

This parameter appears when you set Normalization method to Average Power.

Peak power, referenced to 1 ohm (watts) — Maximum power

1 (default) | positive scalar

Maximum power of the symbols in the constellation in watts, specified as a positive scalar. Power values assume a nominal impedance of 1 ohm.

Dependencies

This parameter appears when you set Normalization method to Peak Power.

View Constellation — Option to plot reference constellation

button

Click View Constellation on the block mask to visualize a signal constellation for the specified block parameters. Before viewing a constellation, apply the parameter settings. For more information, see View Constellation of Modulator Block.

Data Types

Output data type — Output data type

double (default) | single | fixdt(1,16) | fixdt(1,16,0) | Inherit: Inherit via back propagation | <data type expression>

Output data type, specified as double, single, fixdt(1,16), fixdt(1,16,0), Inherit: Inherit via back propagation, or <data type expression>.

• fixdt(1,16), fixdt(1,16,0), or <data type expression> enables parameters in which you can further specify details.

• Inherit: Inherit via back propagation sets the output data type and scaling to match the following block.

For information about specifying data types, see Data Type Assistant.

Block Characteristics

Data Types	Boolean | double | fixed pointa, b | integer | single
Multidimensional Signals	no
Variable-Size Signals	yes
a ufix(1) at the input if ''input type'' is set to ''bit''. ufix(ceil(log2(M))) at input if ''input type'' is set to ''integer'' for M-ary modulation. b Fixed-point outputs must be signed.

More About

Data Type Assistant

The Data Type Assistant helps you set data attributes. To use the Data Type Assistant, click . For more information, see Specify Data Types Using Data Type Assistant (Simulink).

Algorithms

Constellation Size and Scaling

The block outputs the real-valued constellation symbols as a complex signal with the imaginary part equal to zero. Constellation symbols map an integer m in the range [0, (M – 1)] to the complex value 2m – M + 1. M is the modulation order as specified by the M-ary number parameter.

The block scales the default signal constellation based on the setting of the Normalization method parameter. This table lists the possible scaling conditions.

Value of Normalization Method Parameter	Scaling Condition
Min. distance between symbols	The nearest pair of points in the constellation is separated by the value of the Minimum distance parameter.
Average Power	The average power of the symbols in the constellation is the value of the Average power, referenced to 1 ohm (watts) parameter.
Peak Power	The maximum power of the symbols in the constellation is the value of the Peak power, referenced to 1 ohm (watts) parameter.

The Plot M-PAM Constellation in Simulink example demonstrates the constellation scaling based to normalization method.

The Constellation ordering parameter specifies whether the block assigns signal constellation points using binary-coded or Gray-coded mapping. For details about Gray coding and symbol mapping, see Digital Baseband Modulation and View Constellation of Modulator Block.

Integer-Valued Signals and Binary-Valued Signals

This block accepts a scalar or column vector input signal.

When you set the Input type parameter to Integer, the block accepts integer values in the range [0, (M-1)]. M is the modulation order as specified by the M-ary number block parameter.

When you set the Input type parameter to Bit, the block accepts binary-valued inputs that represent integers. The block collects binary-valued signals into groups of K = log₂(M) bits, where K is the number of bits per symbol and M is the modulation order. The input vector length must be an integer multiple of K. In this configuration, the block accepts a group of K bits and maps that group onto a symbol at the block output. The block outputs one modulated symbol for each group of K bits.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using Simulink® Coder™.

Version History

Introduced before R2006a