Modulate using differential quaternary phase shift keying method
PM, in Digital Baseband sublibrary of Modulation
The DQPSK Modulator Baseband block modulates using the differential quaternary phase shift keying method. The output is a baseband representation of the modulated signal.
The input must be a discretetime signal. For information about the data types each block port supports, see Supported Data Types.
When you set the Input type parameter to Integer
,
the valid input values are 0, 1, 2, and 3. In this case, the block
accepts a scalar or column vector input signal. If the first input
is m, then the modulated symbol is
exp(jθ + jπm/2)
where θ represents the Phase rotation parameter. If a successive input is m, then the modulated symbol is the previous modulated symbol multiplied by exp(jθ + jπm/2).
When you set the Input type parameter to Bit
,
the input contains pairs of binary values. In this case, the block
accepts a column vector whose length is an even integer. The following
figure shows the complex numbers by which the block multiples the
previous symbol to compute the current symbol, depending on whether
you set the Constellation ordering parameter
to Binary
or Gray
.
The following figure assumes that you set the Phase rotation parameter
to $$\frac{\Pi}{4}$$; in other cases, the two schematics
would be rotated accordingly.
The following figure shows the signal constellation for the
DQPSK modulation method when you set the Phase rotation parameter
to $$\frac{\Pi}{4}$$. The arrows indicate the four
possible transitions from each symbol to the next symbol. The Binary
and Gray
options
determine which transition is associated with each pair of input values.
More generally, if the Phase rotation parameter has the form $$\frac{\Pi}{k}$$for some integer k, then the signal constellation has 2k points.
Indicates whether the input consists of integers or pairs of bits.
Determines how the block maps each pair of input bits to a corresponding integer, using either a Binary or Gray mapping scheme.
The phase difference between the previous and current modulated symbols when the input is zero.
The output data type can be either single
or double
.
By default, the block sets this to double
.
Port  Supported Data Types 

Input 

Output 
