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3-24
Making Time Domain Measurements
Transforming CW Time Measurements into the Frequency Domain
Figure 3-19 Separating the Amplitude and Phase Components of
Test-Device-Induced Modulation
Forward Transform Range
In the forward transform (from CW time to the frequency domain), range is defined as the
frequency span that can be displayed before aliasing occurs, and is similar to range as
defined for time domain measurements. In the range formula, substitute time span for
frequency span.
For the example, a 201 point CW time measurement made over a 200 ms time span, choose
a span of 1 kHz or less on either side of the center frequency (see Figure 3-20). That is,
choose a total span of 2 kHz or less.
Range
Number of points
1–
time span
-------------------------------------------------------------=
Range
201 1–
200 10
3–
×
--------------------------=
Range
1000 Hertz
=