User manual
Mathematics
R&S
®
RTO
197User Manual 1316.0827.02 ─ 06
d) Define the resolution bandwidth for the FFT result.
The resolution bandwidth defines how precise the results are, i.e. how close
together the individual frequencies can be. Small values result in a high precision,
as the distance between two distinguishable frequencies is small. Higher values
decrease the precision, but increase performance.
3. Select the most suitable "Window type" for your source data. Window functions are
multiplied with the input values and thus can improve the FFT display. For details,
see "Window type" on page 201.
4. Select an arithmetic mode for the FFT frames. This mode defines how the individual
frame results are combined to a final FFT waveform.
5. Select an overlap factor for neighboring frames.
The higher the overlap factor, the more frames are used. This leads to more individual
results and improves detection of transient signal effects. However, it also extends
the duration of the calculation.
To configure magnitude results
1. Open the "FFT Magnitude/Phase" tab of the "Math" dialog box.
2. Select the scaling unit. Use logarithmic scaling only for input values in Volt or Watt.
3. Decide whether you want to configure the value range manually or use the automatic
settings by tapping the corresponding icon.
4. In manual mode, define the size of the "Vertical range" and the "Vertical maximum"
to be displayed.
5. In automatic mode, define the size of the "Range" to be displayed.
6. For logarithmic scaling in dB, also define the "Reference level" to be used.
To configure phase results
1. Open the "FFT Magnitude/Phase" tab of the "Math" dialog box.
2. Select the scaling unit.
3. To eliminate phase shifts due to a limitation of the value range, enable the
"Unwrap" function.
4. To suppress small phase values due to noise, enable the "Suppression" function and
enter a "Threshold" value.
To restrict the input values (gating)
1. In the "FFT Gating" tab of the "Math" dialog box, define the gate area, i.e. the extract
of the time base in the original diagram for which the FFT analysis is to be performed.
To do so, use one of the following methods:
● Select the "Absolute" mode and enter the "Start" and "Stop" times that define the
gate area.
FFT Analysis