Communications Blockset    
M-DPSK Demodulator Baseband

Demodulate DPSK-modulated data

Library

PM, in Digital Baseband sublibrary of Modulation

Description

The M-DPSK Demodulator Baseband block demodulates a signal that was modulated using the M-ary differential phase shift keying method. The input is a baseband representation of the modulated signal. The input and output for this block are discrete-time signals. The input can be either a scalar or a frame-based column vector.

The M-ary number parameter, M, is the number of possible output symbols that can immediately follow a given output symbol. The block compares the current symbol to the previous symbol. The block's first output is the initial condition of zero (or a group of zeros, if the Output type parameter is set to Bit) because there is no previous symbol.

Binary or Integer Outputs

If the Output type parameter is set to Integer, then the block maps a phase difference of

to m, where is the Phase offset parameter and m is an integer between 0 and M-1.

If the Output type parameter is set to Bit and the M-ary number parameter has the form 2K for some positive integer K, then the block outputs binary representations of integers between 0 and M-1. It outputs a group of K bits, called a binary word, for each symbol.

In binary output mode, the Constellation ordering parameter indicates how the block maps an integer to a corresponding group of K output bits. See the reference pages for the M-DPSK Modulator Baseband and M-PSK Modulator Baseband blocks for details.

Processing an Upsampled Modulated Signal

The input signal can be an upsampled version of the modulated signal. The Samples per symbol parameter is the upsampling factor. If it is greater than 1, then the demodulated signal is delayed by one output sample. For more information, see Upsampled Signals and Rate Changes in Using the Communications Blockset.

Dialog Box

M-ary number
The number of possible modulated symbols that can immediately follow a given symbol.
Output type
Determines whether the output consists of integers or groups of bits.
Constellation ordering
Determines how the block maps each integer to a group of output bits. This field is active only when Output 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 input samples that represent each modulated symbol.

Pair Block

M-DPSK Modulator Baseband

See Also

DBPSK Demodulator Baseband, DQPSK Demodulator Baseband, M-PSK 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.


  Matrix Interleaver M-DPSK Demodulator Passband