Configuring the internal baseband source
R&S
®
SMM100A
233
User Manual 1179.1341.02 ─ 05
4.10.2.2
Optimizing the crest factor
An introduction to the topic is provided in
Chapter 4.4.1.7, "Methods for optimizing the
on page 106. This section focuses on the settings provided for and rela-
ted to the multicarrier signals.
The R&S
SMM100A provides a crest factor reduction in form of an automatic optimiza-
tion upon selected values for the following parameters:
●
Crest factor optimization mode
: determines whether the phase settings are
selectable or internally calculated to fulfill a requirement for the crest factor value.
●
Clipping:
reduces the peak power of the resulting multicarrier signal according to
the input parameter "Target Crest Factor"
The resulting clipped peak power is the sum of the RMS level of the unclipped mul-
ticarrier signal and the parameter "Target Crest Factor".
Because clipping reduces also the RMS level, the resulting crest factor of the clip-
ped signal is slightly above the "Target Crest Factor".
●
Target crest factor:
determines the target crest factor. A value above the crest
factor of the unclipped multicarrier signal has no effect.
●
Filter cut off frequency:
determines the filter parameter of the final lowpass filter.
When the cutoff frequency is set as half of the output sample rate, a final lowpass
filter improves the spectrum of the clipped multicarrier signal. However, it can also
increase the resulting crest factor.
4.10.3
Multi-carrier settings
Access:
► Select "Baseband > ARB > General > Create Multi Carrier".
The "ARB: Multi Carrier" dialog enables direct configuration of the carrier distribu-
tion around the center frequency and adjusting some parameters for improving the
signal characteristics.
The dialog is divided into several tabs. In each case, the current setting is dis-
played in the tab name. The tab "Carrier Table" enables the selection of the wave-
form files to be processed. Use the "Carrier Graph" to visualize the configured sig-
nal.
The remote commands required to define these settings are described in
ter 13.16.4.3, "SOURce:BB:ARBitrary subsystem"
Settings:
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Generating multi-carrier signals