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312 Chapter5
One-Button Measurement Functions
MEASURE (Spectrum Analysis Mode)
One-Button Measurement Functions
5.1.7 Power Stat CCDF
The CCDF measurement is a statistical measurement of a high-level signal or peak power.
It shows in both graphical and tabular form for what percentage of the time a signal
exceeds its average power, and by how much this average is exceeded. For more
information see
“Meas Setup (Complementary Cumulative Distribution Function—CCDF)” on page 381.
For each single sweep of this measurement, the average power is defined by:
where V is the envelope voltage, Z
0
is the characteristic impedance, and n is the number of
samples (32k maximum).
Pavg is used as a guideline to define the probability of the samples, which is xdB above the
average power. The number of samples collected per sweep depends upon the sampling
rate and the setting of the measurement interval. Multiple sweeps may be required if the
sample number exceeds the number of samples collected per sweep. The results and the
CCDF curve are updated after each sweep.
Results from a 2.17 GHz 3GPP W-CDMA input signal are shown below in
Figure 3.
NOTE It is important to set the correct center frequency before initiating this
measurement.
Figure 3 Power Stat CCDF Measurement Results
Pavg V
2
Z
0
⁄()
1
n
n⁄=