Configuring the Internal Baseband Source
R&S
®
SMW200A
383User Manual 1175.6632.02 ─ 30
General principle for composing the multi-carrier signal
The following is a list of the general steps used for composing the multicarrier signal:
●
In the default mode, the up to 512 carriers are equally spaced and centered toward
the RF frequency or the baseband DC line.
The carrier spacing is adjustable within the total available bandwidth. Make sure,
that the total RF bandwidth of the composed multicarrier signal does not exceed
the available RF bandwidth, see data sheet.
●
Another possibility is to define the center frequency of each of the carrier individu-
ally, see also Chapter 5.11.2.1, "Defining the Carrier Frequency", on page 383.
●
Each carrier can be separately defined in terms of power, phase and modulated
input signal.
To define the leveling of the composed multicarrier signal, use the parameter
Power Reference
●
Optionally, crest factor optimization can be applied (see Chapter 5.11.2.2, "Optimiz-
ing the Crest Factor", on page 384).
●
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.
5.11.2.1 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 SMW provides the parameter Mode for this purpose.
Generating Multi-Carrier Signals
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