QPSK Modulator Baseband
Modulate using quadrature phase shift keying method
Library
PM in Digital Baseband sublibrary of Modulation
Description
The QPSK Modulator Baseband block modulates using the quadrature phase shift keying method. The output is a baseband representation of the modulated signal.
Integer-Valued Signals and Binary-Valued Signals
If you set the Input type parameter to
Integer, then valid input values are 0, 1, 2, and 3. When you
set Constellation ordering to Binary for
input m the output symbol is
exp(jθ + jπm/2)
where θ represents the Phase offset parameter (see the following figure for Gray constellation ordering). In this case, the block accepts a scalar or column vector signal.
If you set the Input type parameter to
Bit, then the input contains pairs of binary values. For this
configuration, the block accepts column vectors with even lengths. When you set the
Phase offset parameter to , then the block uses one of the signal constellations in the following
figure, depending on whether you set the Constellation ordering
parameter to Binary or Gray.
In the previous figure, the most significant bit (i.e. the left-most bit), is the first bit input to the block. For additional information about Gray mapping, see the M-PSK Modulator Baseband help page.
Constellation Visualization
The QPSK Modulator Baseband block provides the capability to visualize a signal constellation from the block mask. This Constellation Visualization feature allows you to visualize a signal constellation for specific block parameters. For more information, see the Constellation Visualization section of the Communications Toolbox™ User's Guide.
Dialog Box
- Phase offset (rad)
The phase of the zeroth point of the signal constellation.
- Constellation ordering
Determines how the block maps each pair of input bits or input integers to constellation symbols.
- Input type
Indicates whether the input consists of integers or pairs of bits.
- Output data type
The output data type can be set to
double,single,Fixed-point,User-defined, orInherit via back propagation.Setting this parameter to
Fixed-pointorUser-definedenables fields in which you can further specify details. Setting this parameter toInherit via back propagation, sets the output data type and scaling to match the following block.- Output word length
Specify the word length, in bits, of the fixed-point output data type. This parameter is only visible when you select
Fixed-pointfor the Output data type parameter.- Set output fraction length to
Specify the scaling of the fixed-point output by either of the following methods:
Choose
Best precisionto have the output scaling automatically set such that the output signal has the best possible precision.Choose
User-definedto specify the output scaling in the Output fraction length parameter.
This parameter is only visible when you select
Fixed-pointfor the Output data type parameter or when you selectUser-definedand the specified output data type is a fixed-point data type.- User-defined data type
Specify any signed built-in or signed fixed-point data type. You can specify fixed-point data types using the
sfix(Simulink),sint(Simulink),sfrac(Simulink), andfixdt(Simulink) functions from Fixed-Point Designer™. This parameter is only visible when you selectUser-definedfor the Output data type parameter.- Output fraction length
For fixed-point output data types, specify the number of fractional bits or bits to the right of the binary point. This parameter is only visible when you select
Fixed-pointorUser-definedfor the Output data type parameter andUser-definedfor the Set output fraction length to parameter.
Supported Data Types
| Port | Supported Data Types |
|---|---|
Input |
|
Output |
|