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M-DPSK Modulator Baseband - Modulate using 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. For integer inputs, the block can accept the data types int8, uint8, int16, uint16, int32, uint32, single, and double. For bit inputs, the block can accept int8, uint8, int16, uint16, int32, uint32, boolean, single, and double.

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 k₁, then the modulated symbol is

where θ is the Phase rotation parameter. If a successive input is k, then the modulated symbol is

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. θ is the Phase rotation parameter. The phase difference is between the previous symbol and the current symbol.

Current Input	Binary-Coded Phase Difference	Gray-Coded Phase Difference
[0 0 0]	jθ	jθ
[0 0 1]	jθ + jπ/4	jθ + jπ/4
[0 1 0]	jθ + jπ2/4	jθ + jπ3/4
[0 1 1]	jθ + jπ3/4	jθ + jπ2/4
[1 0 0]	jθ + jπ4/4	jθ + jπ7/4
[1 0 1]	jθ + jπ5/4	jθ + jπ6/4
[1 1 0]	jθ + jπ6/4	jθ + jπ4/4
[1 1 1]	jθ + jπ7/4	jθ + jπ5/4

For more details about the Binary and Gray options, see the reference page for theM-PSK Modulator Baseband block. The signal constellation for that block corresponds to the arrangement of phase differences for this block.

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.
Phase rotation (rad): The phase difference between the previous and current modulated symbols when the input is zero.
Output data type: The output data type can be either single or double. By default, the block sets this to double.

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.