Configuring the Internal Baseband Source
R&S
®
SMBV100B
225
User Manual 1178.4460.02 ─ 03
●
After all multi-carrier processing steps are completed, the instrument calculates the
resulting peak and RMS power over the total signal. This value is then written in
the waveform file.
3.8.2.1
Defining the Carrier Frequency
There are two ways to define the carrier frequency of the individual carriers in the mul-
ticarrier signal:
●
Enabling the
arbitrary carrier frequency
distribution and specifying the carrier fre-
quency of each carrier individually.
●
Using the built-in
equidistant carrier spacing
distribution function.
That is, enabling the carriers to be equally spaced and centered toward the RF fre-
quency. The carrier frequencies are automatically calculated depending on the
selected number of carriers and the carrier spacing.
The maximum carrier spacing is a function of the available total bandwidth and the
selected number of carriers. It is calculated as follows:
Max Carrier Spacing = Total bandwidth /(Number of Carriers - 1)
To avoid wrap-around problems, the effective applied carrier spacing can be
slightly modified.
The value of the carrier spacing is rounded in that way that the carrier closest to
the center RF frequency shows no phase jump. It is assumed that the carrier is
unmodulated.
–
For odd number of carriers:
RoundedCarrierSpacing
=
1/OutputSignalDuration*round(CarrierSpac-
ing*OutputSignalDuration)
–
For even number of carriers:
RoundedCarrierSpacing
=
2/OutputSignalDuration*round(0.5*CarrierSpac-
ing*OutputSignalDuration)
The R&S
SMBV100B provides the parameter
3.8.2.2
Optimizing the Crest Factor
An introduction to the topic is provided in
Chapter 3.4.1.7, "Methods for Optimizing the
on page 107. This section focuses on the settings provided for and rela-
ted to the multicarrier signals.
The R&S
SMBV100B provides a crest factor reduction in form of an automatic optimi-
zation 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".
Generating Multi-Carrier Signals
