Communications Blockset

M-PAM Modulator Baseband

Modulate using M-ary pulse amplitude modulation

Library

AM, in Digital Baseband sublibrary of Modulation

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.

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 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 table below 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

Input Signal Values

The input and output for this block are discrete-time signals. The Input type parameter determines whether the block accepts integers between 0 and M-1, or binary representations of integers.

• If Input type is set to Integer, then the block accepts integers. The input can be either a scalar or a frame-based column vector.
• If Input type is set to Bit, then the block accepts groups of K bits, called binary words. The input can be either a vector of length K or a frame-based column vector whose length is an integer multiple of K. 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.

Upsampling the Modulated Signal

This block can output an upsampled version of the modulated signal. The Samples per symbol parameter is the upsampling factor. It must be a positive integer. For more information, see Upsampled Signals and Rate Changes in Using the Communications Blockset.

Dialog Box

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. This field is active only when Input type is set to Bit.

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 (watts)

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

Peak power (watts)

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

Samples per symbol

The number of output samples that the block produces for each integer or binary word in the input.

Pair Block

M-PAM Demodulator Baseband

See Also

General QAM Modulator Baseband

M-PAM Demodulator Passband

M-PAM Modulator Passband