110 Keysight WLAN Measurement Guide
Concepts
WLAN Measurement Concepts
Figure 3-12
CCDF Measurement
Measurement Method
The power measured in power statistics CCDF curves is actually instantaneous
envelope power defined by the equation:
(where I and Q are the quadrature voltage components of the waveform and Zo
is the characteristic impedance).
A CCDF curve is defined by how much time the waveform spends at or above a
given power level. The percent of time the signal spends at or above the level
defines the probability for that particular power level. For capturing a lower
probability down to 0.0001%, this measurement is made in the single mode. To
make the power statistics CCDF measurement, the instrument uses digital
signal processing (DSP) to sample the input signal in the channel bandwidth.
The Gaussian distribution line as the band-limited Gaussian noise CCDF
reference line, the user-definable reference trace, and the currently measured
trace can be displayed on a semi-log graph. If the currently measured trace is
above the user reference trace, it means that the higher peak power levels
against the average power are included in the input signal.
P
I
2
Q
2
+
(
)
Z
0
⁄
=