Demodulate OQPSKmodulated data
PM, in Digital Baseband sublibrary of Modulation
The OQPSK Demodulator Baseband block demodulates a signal that was modulated using the offset quadrature phase shift keying method. The input is a baseband representation of the modulated signal.
The input must be a discretetime complex signal. This block accepts a scalarvalued or column vector input signal. For information about the data types each block port supports, see Supported Data Types.
When you set the Output type parameter
to Integer
, the block outputs integer symbol
values between 0 and 3. When you set the Output type parameter
to Bit
, the block outputs a 2–bit
binary representation of integers, in a binaryvalued vector with
a length that is an even number.
The block produces one output symbol for each pair of input samples. The input sample period is half the period of each output integer or bit pair. The constellation used to map bit pairs to symbols is on the reference page for the OQPSK Modulator Baseband block.
In singlerate processing mode, the input and output signals have the same port sample time. The block implicitly implements the rate change by making a size change at the output when compared to the input. The input can be an even length column vector.
When you set Output type to Bit
,
the output width is 2 times the number of input symbols.
When you set Output type to Integer
,
the output width is the number of input symbols.
To open this modelopen this model,
type doc_moqpskdemod_fb
at the MATLAB^{®} command
line.
In multirate processing mode, the input and output signals have different port sample times. The input must be a scalar. The output symbol time is two times the input sample time.
When you set Output type to Bit
,
the output width equals 2.
When you set Output type to Integer
,
the output is a scalar.
To open this modelopen this model, type doc_moqpskdemod_sb at the MATLAB command line.
The modulatordemodulator pair incurs a delay, as described in Example: Delays from Demodulation.
OQPSK FixedPoint Signal Flow Diagram
Note: Every two input samples produce one output symbol. In the preceding figure, the dotted line represents the region comprised of input sample processing. 
OQPSK Floating Point Signal Flow Diagram
Note: Every two input samples produce one output symbol. In the preceding figure, the dotted line represents the region comprised of input sample processing. 
The amount by which the phase of the zeroth point of the signal constellation is shifted from π/4.
Determines whether the output consists of integers or pairs of bits.
Select the rate processing option for the block.
Enforce singlerate processing
—
When you select this option, the input and output signals have the
same port sample time. The block implements the rate change by making
a size change at the output when compared to the input. The output
width equals half the input width for integer outputs.
Allow multirate processing
—
When you select this option, the input and output signals have different
port sample times. The output symbol time is two times the input sample
time.
Note:
The option 
Data Type Pane
For bit outputs, the output data type can be set to 'Inherit
via internal rule'
, 'Smallest unsigned integer'
, double
, single
, int8
, uint8
, int16
, uint16
, int32
, uint32
,
or boolean
.
For integer outputs, the output data type can be set to 'Inherit
via internal rule'
, 'Smallest unsigned integer'
, double
, single
, int8
, uint8
, int16
, uint16
, int32
,
or uint32
.
When this parameter is set to 'Inherit via internal
rule'
(default setting), the block will inherit the output
data type from the input port. The output data type will be the same
as the input data type if the input is a floatingpoint type (single
or double
).
If the input data type is fixedpoint, the output data type will work
as if this parameter is set to 'Smallest unsigned integer'
.
When this parameter is set to 'Smallest unsigned integer'
,
the output data type is selected based on the settings used in the Hardware
Implementation pane of the Configuration Parameters dialog
box of the model.
If ASIC/FPGA
is selected in the Hardware
Implementation pane, and Output type is Bit
,
the output data type is the ideal minimum onebit size, i.e., ufix1
.
For all other selections, it is an unsigned integer with the smallest
available word length large enough to fit one bit, usually corresponding
to the size of a char (e.g., uint8
).
If ASIC/FPGA
is selected in the Hardware
Implementation pane, and Output type is Integer
,
the output data type is the ideal minimum twobit size, i.e., ufix2
.
For all other selections, it is an unsigned integer with the smallest
available word length large enough to fit two bits, usually corresponding
to the size of a char (e.g., uint8
).
This parameter only applies when the input is fixedpoint and Phase offset is not a multiple of $$\frac{\Pi}{2}$$.
This can be set to Same word length as input
or Specify
word length
, in which case a field is enabled for user input.
Specify the data type for the Accumulator. You can set this
parameter to Inherit via internal rule
, Same
as input
or Binary point scaling
.
The Accumulator parameter only applies for fixedpoint inputs. The selections you make for the Rounding and Overflow parameters affect the Accumulator.
Fixedpoint Communications System Toolbox blocks that must hold summation results for further calculation usually allow you to specify the data type and scaling of the accumulator. Most such blocks cast to the accumulator data type prior to summation:
Use the Accumulator—Mode parameter to specify how you would like to designate the accumulator word and fraction lengths:
When you select Inherit via internal
rule
, the accumulator output word and fraction lengths
are automatically calculated for you. Refer to Inherit via Internal Rule for
more information.
When you select Same as product output
,
these characteristics match those of the product output.
When you select Same as input
,
these characteristics match those of the first input to the block.
When you select Binary point scaling
,
you are able to enter the word length and the fraction length of the
accumulator, in bits.
When you select Slope and bias scaling
,
you are able to enter the word length, in bits, and the slope of the
accumulator. The bias of all signals in DSP System Toolbox™ software
is zero.
The block uses the Rounding method when the result of a fixedpoint calculation does not map exactly to a number representable by the data type and scaling storing the result. For more information, see Rounding Modes in DSP System Toolbox User's Guide or Rounding Mode: Simplest in the FixedPoint Designer™ documentation.
Specify the method of storing the result when the magnitude
of a fixedpoint calculation result that does not does not fit within
the range of the data type selected. You can select either Wrap
or Saturate
for
this parameter.
For more information refer to Overflow in the Precision and Range subsection of DSP System Toolbox.
This can be set to Same as accumulator
or Binary
point scaling
. This parameter only applies for fixedpoint
inputs.
Port  Supported Data Types 

Input 

Output 
