OQPSK Demodulator Baseband
Demodulation using OQPSK method
- Library:
Communications Toolbox / Modulation / Digital Baseband Modulation / PM
Description
The OQPSK Demodulator Baseband block applies pulse shape filtering to the input waveform and demodulates it using the offset quadrature phase shift keying (OQPSK) method. For more information, see Pulse Shaping Filter. The input is a baseband representation of the modulated signal.
For information about delays incurred by modulator-demodulator pair processing, see Modulation Delays.
Ports
Input
Output
Parameters
Modulation
Output type — Output type
Integer (default) | Bit
Output type, specified as Integer or
Bit.
When you set Output type to
Integer, the block outputs a vector of integer symbols with values from 0 to 3, the length of which is the number of output symbols.When you set Output type to
Bit, the block outputs a 2-bit binary representation of integers, in a binary-valued, even-length vector.
The input period for each integer or bit pair is the Samples per symbol times the output sample period.
Phase offset (rad) — Phase of zeroth point of signal constellation
0 (default) | scalar
Phase offset from π/4, specified as a scalar in radians. The phase offset is applied to the zeroth point of the signal constellation before delay of quadrature component. After the OQPSK imaginary-component delay the signal is normalized with unity power.
Example: Setting Phase offset (rad) to
pi/4 aligns the zeroth point of the QPSK signal
constellation point on the axes, {(1,0), (0,j), (-1,0),
(0,-j)}.
Symbol mapping — Signal constellation bit mapping
Gray (default) | Binary | custom 4-element numeric vector of integers with values from 0 to
3
Signal constellation bit mapping, specified as
Gray, Binary,
or a custom 4-element numeric vector of integers with values from 0 to
3.
| Setting | Constellation Mapping for Integers | Constellation Mapping for Bits | Comment |
|---|---|---|---|
|
|
| The signal constellation mapping is Gray-encoded. |
|
|
| The signal constellation mapping for the input integer
|
Custom 4-element numeric vector of integers with values from 0 to 3 |
|
| Elements [a b c d] must be composed of the set of values [0, 1, 2, 3] in any order. |
Filtering
Pulse shape — Filtering pulse shape
Half sine (default) | Normal raised cosine | Root raised cosine | Custom
Select the filtering pulse shape: Half
sine, Normal raised cosine,
Root raised cosine, or
Custom.
Rolloff factor — Raised cosine filter rolloff factor
0.2 (default) | scalar
Raised cosine filter rolloff factor, specified as a scalar from
0 to 1.
Dependencies
This property is enabled when Pulse shape is Normal raised
cosine or Root raised
cosine.
Data Types: double
Filter span (in symbols) — Filter length
10 (default) | scalar
Filter length in symbols, specified as a scalar. An ideal raised cosine filter has an infinite impulse response. However, to realize a practical implementation of this filter, the object truncates the impulse response to Filter span (in symbols) symbols.
Dependencies
This property is enabled when Pulse shape is Normal raised
cosine or Root raised
cosine.
Data Types: double
Filter numerator — Filter numerator
[0.7071 0.7071] (default) | row vector
Filter numerator, specified as a row vector.
Dependencies
This parameter is enabled when Pulse shape is Custom.
Data Types: double
Samples per symbol — Number of samples per symbol
4 (default) | positive even integer
Number of samples per symbol, specified as a positive even integer.
Data Types: double
Other Parameters
Rate options — Processing rate option
Enforce single-rate
processing (default) | Allow multirate processing
Enforce single-rate processing— Executes the model, ensuring that 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. For integer outputs, the output width equals 1/Samples per symbol times the input width.For more information, see Single-Rate Processing with OQPSK Demodulator Block.
Allow multirate processing— Executes the model, allowing the input and output signals to have different port sample times. The output symbol time is Samples per symbol times the input sample time.For more information, see Multirate Processing with OQPSK Demodulator Block.
Output data type — Output data type
double (default) | single | uint8
Select the output data type: double,
single, or
uint8.
Model Examples
Block Characteristics
Data Types |
|
Multidimensional Signals |
|
Variable-Size Signals |
|
More About
OQPSK Signal Flow Diagram
Every Samples per symbol input samples produce one output symbol. In this figure, the dotted line represents the region comprising the input sample processing.
