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Design Notes

CCDF Measurement

This example shows a VSS Complementary Cumulative Distribution Function (CCDF) measurement through the use of a:

• QPSK Source

• OQPSK Source

• Multilevel QAM Source

The measurement can be found in measurement type System/Statistics.

Each source has it average signal power set to -40dBW.

The CCDF curve describes the statistical behavior of a signal. It shows how often a particular power level is exceeded. In this example, the y-axis is constrained between 0 and 1. The probability that the signal power will exceed 0 is one. In other words, for zero power the CCDF is always equal to 100%.

In this example, the CCDF shows for 16QAM (brown) that the signal power will exceed the average power by 3dB with a probability of 0.1.

You can monitor the impact on the CCDF as you tune the constellation size of the MQAM source. The choices of constellation sizes are defined in the Global definitions window.

System Diagram - CCDF Measurement System

Graph - CCDF