Rohde & Schwarz R&S UPP, Руководство пользователя

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Instrument Functions
R&S
®
UPP
396 User Manual 1411.1055.32 ─ 10
Post FFT ← Fnct Settling
See section Chapter 5.26, "FFT Analysis" , on page 408 for description of the settings
and associated remote control commands.
Avg Mode ← Fnct Settling
See chapter Chapter 5.26.4, "FFT Measurement Function" , on page 412 for descrip-
tion of the settings and associated remote control commands.
5.23.4 MOD DIST
Mod Dist is a modulation factor analysis which determines the intermodulation of a low-
frequency (dominant) interfering signal to a high-frequency useful signal. According to
IEC 60268 Part 3, the interfering signal should be 60
Hz and the useful signal should
be 7 kHz; the amplitude ratio should preferably be 4 : 1. The R&S UPP measures the
2nd and 3rd order intermodulation products selectively (measurements are therefore
largely unaffected by noise) and calculates their square sum. Contrary to the recom-
mendation in IEC 60268, the
total intermodulation factor is therefore measured to
ensure that this measurement method is comparable to the customary SMPTE mea-
surement method.
The measurement algorithm is highly tolerant with respect to the level ratio of the inter-
fering signal to the useful signal. The level of the interfering signal is allowed to reach
up to 48
dB below the level of the (higher-frequency) useful signal. The level of the
useful signal may be max. 68 dB lower than that of the interfering signal.
The "Mod Dist" signal function of the internal universal generator is recommended as
the
signal source . This allows the frequencies of the interfering and useful signal as
well as their amplitude ratio to be varied. Furthermore, it is also possible to sweep the
total level and useful frequency.
Distortion Measurements