To create a fixed-length waterfall display
There are several computer programs that let you create arbitrary
waveforms (such as MATLAB or MATRIXx). If the waveform is a long
waveform (it contains more than 4096 complex points or 8192 real points),
you must create a waterfall or spectrogram display on the analyzer, copy
the waterfall or spectrogram data to your computer, and use the Standard
Data Format (SDF) utilities to replace the waterfall or spectrogram data
with the data from your computer program. The waterfall or spectrogram
data must have the same sample frequency, length, and ∆t (time-interval
between points) as your computer-generated waveform.
This procedure shows you how to create a waterfall or spectrogram display
that contains the number of samples and ∆t that you need. See ‘’To
create a long waveform using ASCII data’’ to learn how to perform the
remaining steps.
This procedure configures the analyzer to create a waterfall display for a
complex signal that has a sample frequency of 3.84 MHz and a total source
length of 5ms. Substitute your values where necessary.
1. Initialize the analyzer and select the Vector instrument mode:
Press [
Instrument Mode
], [
receiver
], then press:
89410A: [
input section (0-10 MHz)
].
89441A: [
RF section (0-10 MHz)
].
Press [
Preset
].
Press [
Instrument Mode
], [
Vector
].
2. Set the rbw mode to arbitrary and rbw coupling to auto:
Press [
ResBW/Window
], [rbw mode arb], [rbw coupling auto], [Return].
3. Compute the total number of samples in the waveform:
Total Samples = 3.84
Msamples
sec
× 5 ms = 19,200 samples
4. Divide the total number of samples into N equal-length segments. Note that:
l
Each segment must contain an integer number of samples:
l
For real signals, each segment must have between 128 and 8192 samples.
l
For complex (zoom) signals, each segment must have between 64 and 4096
samples.
For this example, there are several possible solutions, such as:
10 segments of 1920 samples.
12 segments of 1600 samples.
20 segments of 960 samples.
Creating Arbitrary Waveforms
6-12
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