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Measurement of the CCDF (complementary cumulative distribution function) is often used for evaluating nonlinearities of amplifiers or transmitter output stages, for instance (see also refresher topic on page 44). This measurement indicates how often the observed signal reaches or exceeds
a specific level. From a physical point of view, the CCDF measurement is the integral of the distribution function versus the level (integration of the observed level to infinity). Comparison of measured values and theoretical reference values (which can be determined for OFDM or mQAM/ VSB) quickly yields information on the nonlinear response of all types of active elements. However, the great advantage of the CCDF measurement is that the useful signal itself is analyzed; as a result, it is not necessary to
transmit complex test sequences. This test tip compares two different measurement methods.
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