SMIQ
Digital Standard 3GPP W-CDMA (FDD)
1125.5555.03
E-9
2.191
2.14.2.3 WCDMA/3GPP Menu - Display of CCDF
Fig. 2-111
DIGITAL STD – WCDMA/3GPP – CCDF menu with a trace
A complementary cumulative distribution function" can be generated from the filtered I/Q samples. This
function gives the probability of the magnitude of a complex sample exceeding a predefined threshold.
The complete waveform, i.e. the sum for all (max. 4) stations is used to calculate the CCDF.
If this threshold is thought of as the radius of a circle centered on the origin, the radius is plotted along the
horizontal axis and the probability of the samples lying outside this circle along the vertical axis. Only radii
that correspond to values that are at least as great as the average power are considered.
The crest factor can be read off at the intersection of the trace with the x axis. The precise value is
obtained from the displayed levels (PEP-LEVEL).
Fig. 2-112
Reading off the crest factor from LEVEL displays
In this example, the crest factor is 7.8 dB.
The number of simultaneously displayed traces can be set with the menu item NUMBER OF CCDF
TRACES. Displaying several traces shows the effect of the parameters on the envelope. The baseband
filter, the timing offsets and the channelization codes in particular have an effect on the CCDF.
The last three traces are distinguished in the following way:
Current trace:
Last trace:
Last but one trace:
Fig. 2-113
DIGITAL STD – WCDMA/3GPP – CCDF menu with three traces
