Rohde & Schwarz R&S UPP, User Manual

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Instrument Functions
R&S
®
UPP
411 User Manual 1411.1055.32 ─ 10
"Rife Vincent
x" The suppression of far-off interference is very good for all 3 windows.
The width of the bell-shaped curve at the bottom of the individual
lines drops and the width at the top increases as the Rife Vincent
number increases. It is therefore possible to set various compromises
between frequency resolution and the suppression of adjacent lines.
Recommended application: For exact determination of frequency
"Hamming" This window does not provide any significant advantages; it was
implemented simply to complete the range.
"Flat Top" Only for Function FFT.
Here, the region around the carrier is deliberately distorted to such an
extent that at least two adjacent lines (in the case of excitation with
one sine-wave line only) always have roughly the same magnitude.
This allows the amplitude to be read off very precisely from the graph.
In contrast, the frequency selectivity is rather poor.
Recommended application: For exact determination of level
Remote command:
SENSe[1]:FUNCtion:FFT:WINDow
on page 763
5.26.3 Post FFT
For distortion measurements, the Post FFT displays the frequency spectrum recorded
for calculating the measured values. It can be activated for the measurement functions
THD+N
& SINAD, THD, DFD and Mod Dist, ChirpBased Meas and RMS measure-
ments.
Measurement is performed in the same level as the associated measurement function,
i.e. downstream of all filters.
The respective measurement function adjusts the FFT size and window to its specific
requirements. For example, the required FFT size increases as the signal frequency
decreases. The settings for the Post FFT cannot therefore be selected by the user and
can vary from measurement to measurement.
The Post FFT is calculated with double precision using up to 256 k points, thus ensur-
ing a very high frequency resolution and dynamic range.
The Post FFT of a measurement channel is displayed in the graphical windows "FFT,
Panel 1" or "FFT, Panel 2" either as a magnitude or phase. Since 2 traces are dis-
played in each graphical window, the magnitude and phase of both channels can be
recorded simultaneously.
Post FFT
Used to activate the Post FFT. In addition the "FFT Graph1" graphical window can be
opened from here.
Configuration of the FFT Graph is reserved for the "FFT Graph1 Config" and/or "FFT
Graph2 Config" windows. The actual display takes place in the "FFT Graph1" or "FFT
Graph2" windows.
FFT Analysis