R&S FSH
Spectrum Analyzer Mode
Configuring Spectrum Measurements
Operating Manual 1309.6275.12 - 14
94
C
RMS
If the RMS detector is active, the R&S FSH measures the spectral power over one
pixel. In case of power measurements, the RMS detector always shows the true
power of a signal, regardless of the shape of the signal.
The RMS detector is best for measurements on digitally modulated signals
because it provides stable and true power readings. In combination with a high
sweep time you can increase the display stability even more because the
measurement time for each pixel increases.
Noise measurements also provide stable results if you apply the RMS detector in
combination with a high sweep time.
However, the bandwidth occupied by the signal to be measured should at least
equal the frequency covered by a trace pixel or the selected resolution bandwidth
(whichever is larger). Otherwise, the power the R&S FSH shows is too low
because there are spectral components within the frequency range covered by the
pixel that do not originate from the signal you want to observe (e.g. noise).
To get the true power, the video bandwidth (VBW) should also be greater than the
resolution bandwidth (RBW). Otherwise, an averaging effect caused by video
bandlimiting comes into play before the RMS value is calculated.
The R&S FSH provides automatic selection of the detector. In that case, the R&S FSH
selects the detector that is most suitable for the current trace mode.
Trace mode
Detector
Clear/Write
Auto Peak
Average
Sample
Max Hold
Max Peak
Min Hold
Min Peak
If you select the detector manually, the detector is independent of the trace mode and
will not change.
M
Press the TRACE key.
M
Press the "Detector" softkey.
M
Select the detector you want to use.
If you automatic detector selection is active, the corresponding menu item is
marked by an [X].
