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Phase/Frequency Offset - Apply phase and frequency offsets to complex baseband signal

Library

RF Impairments

Description

The Phase/Frequency Offset block applies phase and frequency offsets to an incoming signal.

This block operates without any delay, and accepts real and complex inputs of data type double or single. Its output data type matches that of its input.

Phase Offset

The block applies a phase offset to the input signal, specified by the Phase offset parameter.

Frequency Offset

The block applies a frequency offset to the signal that is specified by the Frequency offsetparameter. Alternatively, this information may be provided to the block through an input port that is enabled when the Frequency offset from port checkbox is selected.

The block supports signals of single-samples, multiple-sample single-channel frames, single-sample multi-channel frames, and multi-sample multi-channel frames. The two block parameters can be scalars, vectors, or matrices, as appropriate with the input signal's dimensions. If the input and frequency signals are both frame-based, they must both have the same frame size. If the frequency signal is multi-channel, it must have either one channel or the same number of channels as the input signal. If it is not a scalar, the number of samples in the channel must match the input signal.

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 set to 20 and Frequency offset set to 0:

Observe that each point in the constellation is rotated by a 20 degree angle counterclockwise.

If you set Frequency offset to 2 and Phase offset 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.

I/O Ports

Only 1-D (unoriented) and 2-D ports are supported, as well as 2-D frame-based (single or multichannel) ports.

Scalar (length-one) sample-based data ports are also supported, but nonscalar sample-based ports are not.

Interdependent Parameter-Port Dimensions Table

Data I/O Frmstat	No. of Dim.	Data I/O Dim.	Frame Size	No. of Channels	Freq. or Phase Offset Parameter Dim.
Any	Any	Scalar	1	1	Scalar
Frame-based	2	M x 1	M	1	M, M x 1, 1 x M, 1, 1 x 1
Frame-based	2	1 x N	1	N	N, N x 1, 1 x N, 1, 1 x 1
Frame-based	2	M x N	M	N	M x N, N, N x 1, 1 x N, 1, 1 x 1
Sample-based	2	M x 1 (Errors — not currently supported)
Sample-based	2	1 x N (Errors — not currently supported)
Sample-based	2	M x N (Errors — not currently supported)
Sample-based	1	L (Errors — not currently supported)

Dialog Box

Frequency offset from port: Selecting this option opens a port on the block through which you can input the frequency offset information.
Frequency offset: Specifies the frequency offset in hertz.
Phase offset: Specifies the phase offset in degrees.

If Frequency offset and Phase offset are both vectors or both matrices, their dimensions (vector lengths, or number of rows and columns) must be the same.