Bird Technologies 5019D-Manual - Manual (Page 25)

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Complementary Cumulative Distribution Function (CCDF)
Figure 5 CCDF - 100 W Signal - 80 W Threshold -
20% CCDF
CCDF measures the amount of time the power is above a
threshold. Equivalently, it is the probability that any single
measurement will be above the threshold. The WPS samples
the power over a 300 ms window and compares it to a user-
specified threshold, in Watts. The time above the threshold
relative to the total time is the CCDF.
CCDF measurements are most useful for pseudo-random sig-
nals, such as WCDMA, where a high CCDF means that the trans-
mitter is being overdriven. CCDF can also detect amplitude
distortion within an envelope caused by unwanted modulating
signals. In TDMA systems, CCDF indicates the health of power
amplifier stages and their ability to sustain rated power over an
appropriate timeframe. As a trouble-shooting aid, CCDF allows
tracking of trends such as amplifier overdrive (which can cause
dropped calls and high bit error rates).