156 Chapter 4
Basic Digital Operation
Using Waveform Clipping
How Peaks Cause Spectral Regrowth
Because of the relative infrequency of high power peaks, a waveform will have a high peak-to-average
power ratio (see Figure 4-19). Because a transmitter’s power amplifier gain is set to provide a specific
average power, high peaks can cause the power amplifier to move toward saturation. This causes
intermodulation distortion, which generates spectral regrowth.
Figure 4-19 Peak-to-Average Power
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 Figure 4-20). Consequently, spectral regrowth interferes
with communication in the adjacent bands. Clipping can provide a solution to this problem.
Figure 4-20 Spectral Regrowth Interfering with Adjacent Band
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