Making Statistical Power Measurements (Ccdf) - Keysight X Series Measurement Manual

Making Statistical Power Measurements (CCDF)

Complementary cumulative distribution function (CCDF) curves characterize a
signal by providing information about how much time the signal spends at or above a
given power level. The CCDF measurement shows the percentage of time a signal
spends at a particular power level. Percentage is on the vertical axis and power (in
dB) is on the horizontal axis.
All CDMA signals, and W-CDMA signals in particular, are characterized by high
power peaks that occur infrequently. It is important that these peaks are preserved
otherwise separate data channels can not be received properly. Too many peak
signals can also cause spectral regrowth. If a CDMA system works well most of the
time and only fails occasionally, this can often be caused by compression of the
higher peak signals.
The following example shows how to make a CCDF measurement on a W-CDMA
signal broadcasting at 1.96 GHz. (A signal generator is used to simulate a base
station.)
Step
1 Set up the signal
generator.
2 Connect the source RF
OUTPUT to the analyzer
RF INPUT as shown.
3 Select the mode.
4 Preset the analyzer.
Action
a. Setup a W-CDMA down link
signal.
b. Set the frequency to 1.96
GHz.
c. Set the amplitude to
−10 dBm.
• Press Mode, Spectrum
Analyzer.
• Press Mode Preset.
121
Measuring Digital Communications Signals
Making Statistical Power Measurements (CCDF)
Notes