Important Signal Parameters - R&S SGT100A User Manual

®
R&S SGT100A
The
ing an input signal.

7.9.1 Important Signal Parameters

The correct signal processing of the externally supplied input signals in the instrument
requires information of some signal parameters, like sampling rate, crest factor and
signal level, expressed as peak or as RMS level value.
●
Sample rate
The sample rate of the input signal can be defined manually or automatically
retrieved from the input signal.
●
Crest factor
Test setups may require feeding of external signal to the digital/analog input of the
R&S SGT. As a rule, whenever an I/Q signal is transferred between two instru-
ments, the crest factor at the outputs of the "source" instrument has to match with
the crest factor at the inputs of the receiving one.
The crest factor gives the difference in level between the peak level and RMS level
value in dB. The R&S SGT uses the crest factor value for the calculation of power
levels. The general principle is, that the R&S SGT compensates the RMS levels of
the externally supplied signal by the crest factor.
Figure 7-29: Relation between the level settings
In the instrument, level values are represented relative to the full scale.
Fulfilling the prerequisites for a correct signal processing of the externally sup-
plied baseband signal
In the instrument, the crest factor, peak level and RMS level values can be adjusted
in one of the following ways:
●
Adjusted manually
If you know these values, it is best to enter them directly (see
●
Estimated automatically by the internal measurement function
Use the function
nal, estimate the peak level and RMS level and calculate the crest factor out of
them.
Tip: For accurate level measurements, set the measurement period to a time value
that is long enough to capture several periods of the input signal.
●
Determined automatically (digital baseband input only)
The R&S SGT can receive the values from the connected transmitter.
If the external digital signal source is a second Rohde & Schwarz instrument, it sig-
nals the peak level and RMS level of the signal over the digital input interface. To
User Manual 1176.8674.02 ─ 07
Chapter 7.9.2, "BB Input
Auto Level Set
External Baseband Signal - Baseband Input
Block", on page 237 describes the settings for configur-
to trigger the R&S SGT to measure the input sig-
Signal Generator Settings
Crest Factor)
236