User`s guide

Fourier Components 11
-21
In the example Fourier analysis specification shown in
Figure 11-2 on page 11-15, the voltage waveform at node OUT2
from the transient analysis is to be used and the fundamental
frequency is to be 1 megahertz for the harmonic decomposition.
The period of fundamental frequency is 1 microsecond (inverse
of the fundamental frequency). Only the last 1 microsecond of
the transient analysis is used, and that portion is assumed to
repeat indefinitely. Since V1’s sine wave does indeed repeat
every 1 microsecond, this is sufficient. In general, however, you
must make sure that the fundamental Fourier period fits the
waveform in the transient analysis.