Spectrum analysis
R&S
®
RTE
404User Manual 1326.1032.02 ─ 20
8. If you use an arithmetic mode, increase the "Overlap factor" for neighboring seg-
ments to increase the accuracy of the results.
To restrict the input values (gating)
By default, the FFT is calculated for the entire record length as defined for the data
acquisition. However, you can restrict the time range for which the FFT is calculated,
resulting in a restricted spectrum. Alternatively, the record length can be determined
automatically according to the selected RBW.
1. Select the "FFT Gating" tab of the "Math" dialog box.
2. Determine how the input length is configured by selecting one of the following
options:
● To ensure that the FFT is calculated for the full defined record length, select the
"Record length controlled" option. This option is only available if no gate is
being used ("Use Gate" disabled). The RBW is adapted so that the record
length can be acquired in the specified acquisition time. However, the RBW is
restricted, so that data acquisition may fail if the record length is too long for the
specified acquisition time.
● To couple the used record length to the required RBW, select the "RBW con-
trolled" option. This option is only available if no gate is being used ("Use Gate"
disabled).
The required acquisition time for the defined RBW value is indicated.
● To restrict the basis of the FFT calculation to a certain time base, configure a
time gate, that is: an extract of the time base in the original diagram. To do so,
enable the "Use Gate" option, then do one of the following:
– Select the "Absolute" mode and enter the "Start" and "Stop" times that
define the gate area.
– Select the "Relative" mode and enter the percentages of the total time base
that define the "Relative Start" and "Relative Stop" times.
– If a zoom area has already been defined in the original diagram and you
want to use the same time base for FFT analysis, select "Zoom coupling".
The spectrum waveform displays the spectrum for the specified time span.
To configure magnitude results
1. Open the "FFT Y-Units" tab of the "Math" dialog box.
2. Select the scaling unit. Use logarithmic scaling only for input values in volt or watt.
3. Select if you want to configure the value range manually or use the automatic set-
tings by tapping the corresponding icon.
4. In manual mode, define the size of the "Vertical range" and the "Vertical maximum"
to be displayed.
In automatic mode, define the size of the "Range" to be displayed.
For logarithmic scaling in dB, also define the "Reference level" to be used.
FFT analysis
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