C–7
Using FFT
Spectral power averaging is the technique of choice when
determining the frequency response of passive networks such as
filters. Figures 3 and 4 show the transfer functions of a low pass
filter with a 3 dB cutoff o1 11 MHz obtained by exciting the filter
with a white noise source (Fig. C–3) and a sine swept generator
(Fig. C–4). Both techniques give substantially the same results.
The choice of method is governed by the availability of an
adequate generating source.
The spectra of single time-domain waveforms can be computed
and displayed to obtain power averages obtained over as many
as 50 000 spectra.
Figure C–3
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