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Forward transform
range. In the forward transform (from CW time to the frequency domain),
range is
delIned
as the frequency span that can be displayed before
aiiasing
occurs, and is
similar
to range as defined for time domain measurements. In the range formula, substitute
time span for frequency span.
Example:
Range =
Number of points
-
1
time span
201-
1
= 200 x
10-S
= 1000 Hertz
For the example given above, 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 6-80).
That is, choose a
total
span of 2
kHz
or less.
pged ee-c
Figure
6-80.
Range of a Forward Transform Measurement
lb
increase the frequency domain measurement range, increase the span. The
maximm
range is inversely proportional to the sweep time, therefore it may be necessary to increase
the number of points or decrease the sweep time. Because increasing the number of points
increases the auto sweep time, the
maximm
range is 2
kHz
on either side of the selected CW
time measurement center frequency (4
kHz
total
span). lb display a
total
frequency span of
4
kHz,
enter the span as 4000 Hz.
Application and Operation Concepts
6-145