To determine number of samples and ∆t
If you are using a waterfall or spectrogram display to import data from
your computer-generated waveform, the waterfall or spectrogram must have
the same number of samples and ∆t as your computer-generated waveform,
as explained in “To create a fixed-length waterfall display.”
The time-interval between points (∆t) is calculated according to the
following
formula:∆ t =
1
( frequency span )× n
where n =
1.28 for zoom measurements
2.56 for baseband measurements
The number of points (samples) in a time record is easy to determine with
the right configuration. With [
rbw coupling auto] and [rbw mode arb], the [num freq pts]
softkey determines the number of points, as shown in the following table
(all softkeys are located under the [
ResBW/Window] hardkey).
Time Record Length Using [rbw coupling auto] And [rbw mode arb]
Number of Frequency Points Time-record Length (in points)
(value of [num freq pts] softkey) Zoom Baseband
51 64 128
101 128 256
201 256 512
401 512 1024
801 1024 2048
1601 2048 4096
3201 4096 8192
The numbers in the above table are valid only when [
rbw coupling auto] and
[
rbw mode arb] are selected. For any other combination of rbw coupling
or rbw mode, you must measure the time-record length and use the
following formula to determine the number of samples in a time
record:
Number of points =
Time record length
∆ t
Creating Arbitrary Waveforms
6-14
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