Tektronix RFA300A, User Manual

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Reference
3- 10
RFA300A Measurement Set 8VSB
Peak-to-Average and Channel Spectrum
This section provides a brief overview of the Peak-to-Average and Channel
Spectrum measurement window. For more in-depth information, refer to the
online help.
This window measures the cumulative distribution of peak power over time.
Peak power is the maximum value of envelope power that is randomly reached
by the digitally modulated signal. Power amplifiers driven beyond their
capability cause compression of peaks. This distorts the signal causing out of
channel emissions and lower signal-to-noise ratio.
The measurement is calculated by taking the percentage of time that the signal is
greater than the average amplitude. This measurement and the ideal are both
plotted on the Peak-to-Average graph.
The Peak-to-Average and Channel Spectrum measurement window is shown in
Figure 3--10. The measurement window contains the following areas:
H
Listing of measurement results.
H
A selection control for setting the target operating point in the peak-to-aver-
age graphic. Select the target operating point method in the setup (refer to
Peak-to-Average Setup next).
H
Graphics showing the measured and ideal peak-to-average power curves and
the channel spectrum. The channel spectrum is another tool to assess a
transmitter’s amplitude linearity. To view this graph, click on the Channel
Spectrum tab.
Results listing
Target operating
point control
RFA300A -- Peak / Average & Channel Spectrum
Figure 3- 10: Peak-to-Average and Channel Spectrum measurement window