Rohde & Schwarz R&S UPP, User Manual

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Instrument Functions
R&S
®
UPP
403 User Manual 1411.1055.32 ─ 10
Since nth octave analysis is usually performed in the audio range only, the bandwidth
in the analog analyzer should be set to 22 kHz. This avoids not only needlessly large
FFTs but also long computation times.
A good candidate for use as the excitation signal in the nth octave analysis is the fre-
quency-defined Pink Noise that can be created with the R&S
UPP Generator (see
Chapter 5.6.7, "Random" , on page 249). Unlike white noise, its level roll-off com-
pensates for the apparent level increase encountered with nth octave analysis, which
results from the absolute bandwidth increasing as the frequency increases. If possible
the spacing of the frequency lines on the FFT size should be synchronized ("Spacing
Anlr Track").
Function (Nth Octave)
For selecting FFT based nth octave analysis.
The RMS value of the signal is displayed in the range "Frq Lim Low" to "Frq Lim Upp"
as the measurement result for the function.
Remote command:
SENSe[1]:FUNCtion NOCTave
Meas Mode
This defines the measurement mode and thus implicitly the center frequencies and rel-
ative bandwidth of the bandpass filters.
The center frequencies of the subbands are spaced at intervals of 2
1/n
from the 1 kHz
reference frequency. The exact values can be taken from the Data List bargraph.
The band limits of a subband are at a distance of from the center frequency.
The larger the chosen value of "n" the narrower the bands and the longer the minimum
measurement time.
"Octave" The audio range is divided into octave bands.
"1/3 Octave" The audio range is divided into third octave bands.
"1/6 Octave" The audio range is divided into sixth octave bands.
"1/12 Octave" The audio range is divided into twelfth octave bands.
"1/24 Octave" The audio range is divided into twenty-fourth octave bands. Due to
the extremely narrow bands, analysis is only possible with effect from
21.5 Hz.
Frequency Band Analysis