How Peaks Cause Spectral Regrowth - Agilent Technologies X Series User Manual

Basic Digital Operation (Option 653/655/656/657)
Clipping a Waveform

How Peaks Cause Spectral Regrowth

In a waveform, high power peaks that occur infrequently cause the waveform to have a high
peak–to–average power ratio, as illustrated in the following figure.
Because the gain of a transmitter's power amplifier is set to provide a specific average power, high
peaks can cause the power amplifier to move toward saturation. This causes the intermodulation
distortion that generates spectral regrowth. Spectral regrowth is a range of frequencies that develops
on each side of the carrier (similar to sidebands) and extends into the adjacent frequency bands (see
the following figure). Clipping provides a solution to this problem by reducing the peak–to–average
power ratio.
188 Agilent X-Series Signal Generators User's Guide