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

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HP 8753E manual Range of a Forward Transform Measurement