| Communications Blockset | |
Apply phase and frequency offsets to a complex baseband signal.
Library
Description
The Phase/Frequency Offset block first applies a phase offset and then a frequency offset to a complex, baseband signal. The block performs these operations in the subsystem shown in the following diagram, which you can view by right-clicking the block and selecting Look under mask:
You can view the implementation of the phase or frequency offsets by double-clicking the Phase Offset or Frequency Offset subsystems under the mask.
Phase Offset
The block applies a phase offset to the input signal, specified by the Phase offset (deg) parameter.
Frequency Offset
The block applies a frequency offset to the signal that is specified by the Frequency offset (Hz) parameter.
The effects of changing the block's parameters are illustrated by the following scatter plots of a signal modulated by 16-ary quadrature amplitude modulation (QAM). The usual 16-ary QAM constellation without the effect of the Phase/Frequency Offset block is shown in the first scatter plot:
The following figure shows a scatter plot of an output signal, modulated by 16-ary QAM, from the Phase/Frequency Offset block with Phase offset (deg) set to 20 and Frequency offset (Hz) set to 0:
Observe that each point in the constellation is rotated by a 20 degree angle counterclockwise.
If you set Frequency offset (Hz) to 2 and Phase offset (deg) to 0, the angles of points in the constellation change linearly over time. This causes points in the scatter plot to shift radially, as shown in the following figure:
Note that every point in the scatter plot has magnitude equal to a point in the original constellation.
See Scatter Plot Examples for a description of the model that generates this plot.
Dialog Box
See Also
| | OVSF Code Generator | Phase-Locked Loop | |
