Communications Blockset    
DQPSK Demodulator Baseband

Demodulate DQPSK-modulated data

Library

PM, in Digital Baseband sublibrary of Modulation

Description

The DQPSK Demodulator Baseband block demodulates a signal that was modulated using the differential quaternary phase shift keying method. The input is a baseband representation of the modulated signal.

The input must be a discrete-time complex signal. The output depends on the phase difference between the current symbol and the previous symbol. The first integer (or binary pair, if the Output type parameter is set to Bit) in the block's output is the initial condition of zero because there is no previous symbol.

The input can be either a scalar or a frame-based column vector.

Outputs and Constellation Types

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 0, 1, 2, or 3.

If the Output type parameter is set to Bit, then the output contains pairs of binary values. The reference page for the DQPSK Modulator Baseband block shows which phase differences map to each binary pair, for the cases when the Constellation ordering parameter is either Binary or Gray.

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. It must be a positive integer. For more information, see Upsampled Signals and Rate Changes in Using the Communications Blockset.

Dialog Box

Output type
Determines whether the output consists of integers or pairs of bits.
Constellation ordering
Determines how the block maps each integer to a pair of output bits. This field is active only when Output type is set to Bit.
Phase offset (rad)
This phase difference between the current and previous modulated symbols results in an output of zero.
Samples per symbol
The number of input samples that represent each modulated symbol.

Pair Block

DQPSK Modulator Baseband

See Also

M-DPSK Demodulator Baseband, DBPSK Demodulator Baseband, QPSK Demodulator Baseband


  DPCM Encoder DQPSK Modulator Baseband