Modulate using M-ary pulse amplitude modulation - Simulink

Description

The M-PAM Modulator Baseband block modulates using M-ary pulse amplitude modulation. The output is a baseband representation of the modulated signal. The M-ary number parameter, M, is the number of points in the signal constellation. It must be an even integer.

Note

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

Constellation Size and Scaling

Baseband M-ary pulse amplitude modulation using the block's default signal constellation maps an integer m between 0 and M-1 to the complex value

2m - M + 1

Note

This value is actually a real number. The block's output signal is a complex data-type signal whose imaginary part is zero.

The block scales the default signal constellation based on how you set the Normalization method parameter. The following 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 Average power parameter
`Peak Power`	The maximum power of the symbols in the constellation is the Peak power parameter

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.

The Constellation ordering parameter indicates how the block assigns binary words to points of the signal constellation.

If Constellation ordering is set to Binary, then the block uses a natural binary-coded constellation.
If Constellation ordering is set to Gray, then the block uses a Gray-coded constellation.
For details about the Gray coding, see the reference page for the M-PSK Modulator Baseband block.

Parameters

M-ary number

The number of points in the signal constellation. It must be an even integer.

Input type

Indicates whether the input consists of integers or groups of bits. If this parameter is set to Bit, then the M-ary number parameter must be 2^K for some positive integer K.

Constellation ordering

Determines how the block maps each group of input bits to a corresponding integer.

Normalization method

Determines how the block scales the signal constellation. Choices are Min. distance between symbols, Average Power, and Peak Power.

Minimum distance

The distance between two nearest constellation points. This field appears only when Normalization method is set to Min. distance between symbols.

Average power, referenced to 1 ohm (watts)

The average power of the symbols in the constellation, referenced to 1 ohm. This field appears only when Normalization method is set to Average Power.

Peak power, referenced to 1 ohm (watts)

The maximum power of the symbols in the constellation, referenced to 1 ohm. This field appears only when Normalization method is set to Peak Power.

View Constellation

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.

Output data type

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

Setting this parameter to

fixdt(1,16), fixdt(1,16.0), or <data type expression> enables parameters in which you can further specify details.
Inherit via back propagation sets the output data type and scaling to match the following block.

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

Supported Data Types

Port	Supported Data Types
Input	Double-precision floating point Single-precision floating point Boolean when Input type is `Bit` 8-, 16-, 32-bit signed integers 8-, 16-, 32-bit unsigned integers $u f i x (⌈ \log_{2} M ⌉)$ when Input type is `Integer`
Output	Double-precision floating point Single-precision floating point Signed fixed-point