120 Chapter 3
Basic Digital Operation
Using Waveform Clipping
Figure 3-12 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 3-13). Consequently, spectral
regrowth interferes with communication in the adjacent bands. Clipping can provide a solution to this
problem.
Figure 3-13 Spectral Regrowth Interfering with Adjacent Band
How Clipping Reduces Peak–to–Average Power
You can reduce peak–to–average power, and consequently spectral regrowth, by clipping the waveform
to a selected percentage of its peak power. The PSG vector signal generator provides two different
methods of clipping: circular and rectangular.
During circular clipping, clipping is applied to the combined I and Q waveform (|I + jQ|). Notice in
Figure 3- 14 that the clipping level is constant for all phases of the vector representation and appears
as a circle. During rectangular clipping, clipping is applied to the I and Q waveforms separately (|I|,
|Q|). Notice in Figure 3- 15 on page 122 that the clipping level is different for I and Q; therefore, it
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