M-DPSK Modulator Baseband (Communications Blockset)

Modulate using the M-ary differential phase shift keying method

Library

PM, in Digital Baseband sublibrary of Modulation

Description

The M-DPSK Modulator Baseband block modulates using the M-ary differential phase shift keying method. The output is a baseband representation of the modulated signal. The M-ary number parameter, M, is the number of possible output symbols that can immediately follow a given output symbol.

The input must be a discrete-time signal.

Inputs and Constellation Types

If the Input type parameter is set to Integer, then valid input values are integers between 0 and M-1. In this case, the input can be either a scalar or a frame-based column vector. If the first input is m, then the modulated symbol is

where is the Phase offset parameter. If a successive input is m, then the modulated symbol is the previous modulated symbol multiplied by exp(j + jm/2).

If the Input type parameter is set to Bit and the M-ary number parameter has the form 2^K for some positive integer K, then the block accepts binary representations of integers between 0 and M-1. It modulates each group of K bits, called a binary word. The input can be either a vector of length K or a frame-based column vector whose length is an integer multiple of K.

In binary input mode, the Constellation ordering parameter indicates how the block maps a group of K input bits to a corresponding phase difference. The Binary option uses a natural binary-to-integer mapping, while the Gray option uses a Gray-coded assignment of phase differences. For example, the table below indicates the assignment of phase difference to three-bit inputs, for both the Binary and Gray options. is the Phase offset parameter.

Input
Binary-Coded Phase Differences
Gray-Coded Phase Differences

[0 0 0]
j
j

[0 0 1]
j + j/2
j + j/2

[0 1 0]
j + j2/2
j + j3/2

[0 1 1]
j + j3/2
j + j2/2

[1 0 0]
j + j4/2
j + j6/2

[1 0 1]
j + j5/2
j + j7/2

[1 1 0]
j + j6/2
j + j5/2

[1 1 1]
j + j7/2
j + j4/2

Input	Binary-Coded Phase Differences	Gray-Coded Phase Differences
[0 0 0]	j	j
[0 0 1]	j + j/2	j + j/2
[0 1 0]	j + j2/2	j + j3/2
[0 1 1]	j + j3/2	j + j2/2
[1 0 0]	j + j4/2	j + j6/2
[1 0 1]	j + j5/2	j + j7/2
[1 1 0]	j + j6/2	j + j5/2
[1 1 1]	j + j7/2	j + j4/2

For more details about the Binary and Gray options, see the reference page for the M-PSK Modulator Baseband block. The signal constellation for that block corresponds to the arrangement of phase differences for this 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 possible output symbols that can immediately follow a given output symbol.
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.
Phase offset (rad): The phase difference between the previous and current modulated symbols when the input is zero.
Samples per symbol: The number of output samples that the block produces for each integer or binary word in the input.

Pair Block

M-DPSK Demodulator Baseband

References

[1] Pawula, R. F. "On M-ary DPSK Transmission Over Terrestrial and Satellite Channels." IEEE Transactions on Communications, vol. COM-32, July 1984. 752-761.

M-DPSK Demodulator Passband M-DPSK Modulator Passband