R&S FSH
Spectrum Analyzer Mode
Configuring Spectrum Measurements
Operating Manual 1309.6275.12 - 14
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if you are performing measurements on pulsed signals, the video bandwidth should
be at least three times greater than the resolution bandwidth so that the pulse
edges are not distorted
Like the resolution bandwidth, the video bandwidth has an effect on sweep speed.
Before each measurement, the video filter has to settle.
M
Press the BW key.
M
Press the "Manual VBW" softkey.
The R&S FSH opens an input field to define the video bandwidth.
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Enter the video bandwidth you need.
The R&S FSH uses the video bandwidth you have entered for the measurement.
If the video bandwidth is no longer coupled to the resolution bandwidth, the
R&S FSH puts a red dot at the "VBW" hardware setting (
).
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Press the "Auto VBW" softkey to again couple the video bandwidth to the RBW.
2.2.4 Configuring and Triggering the Sweep
You can find all necessary settings to configure the sweep itself in the sweep menu. To
access it, press the SWEEP key.
2.2.4.1 Setting the Sweep Time
The sweep time is the time it takes the R&S FSH to get the results that are contained
in one trace.
In the frequency domain (span > 0), the sweep time is the time it takes the R&S FSH to
measure the spectrum in the specified span. To avoid the display of spurs in the
spectrum, the sweep time has to meet some conditions.
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The sweep time depends on the resolution bandwidth. If the sweep time is too
short, the resolution filter has no time to settle. In that case, the displayed levels
will be too low. For more information see "
Setting the Resolution Bandwidth
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The sweep depends on the span. If you increase the span, you also have to
increase the sweep time.
In its default state, the R&S FSH couples the sweep time to the span and the
resolution bandwidth to avoid invalid settings. If the coupling is active, the R&S FSH
always sets the shortest possible sweep time to make sure that the display of the
spectrum is correct and valid.
The R&S FSH requires a minimum sweep time of 20 ms for every 600 MHz of span. If
you increase the span, the R&S FSH will also increase the sweep time.
In the time domain (span = 0), the R&S FSH shows the video voltage over time. The
horizontal axis becomes a time axis that starts at 0 s and ends at the sweep time that
you selected. The range of the sweep time in the time domain is from 200
Y
s to 1000 s.
