Instrument Function
R&S
®
SMU200A
338Operating Manual 1007.9845.32 ─ 15
5.8.3.1 Overview and Required Options
The equipment layout for generating the digital modulation signals includes the options
Baseband Main Module (R&S SMU-B13) and Baseband Generator (R&S SMU-B9/B10/
B11).
In the case of two-path instruments, at least one further Baseband Generator (R&S SMU-
B9/B10/B11) option is needed for signal generation in the second path. Using this option
a signal can be defined in path B and then either routed via path A or added to the signal
on path A with a frequency offset that can be set. When path B is fully expanded with a
second option Baseband Main Module (R&S SMU-B13) and an RF section frequency
option (R&S SMU-B20x) the modulation signal can be output on RF output B.
When modulation is ON, a two-part level indication is shown in the header section of the
display. This displays both the average power (LEVEL) and the peak envelope power
(PEP) of the modulated output signal.
The difference between PEP and LEVEL depends on the modulation type and the filter-
ing: Both values are pre-measured internally so that the displayed values match the true
values in the signal. When external signals are used, they are replaced by PRBS data
during pre-measurement.
5.8.3.2 Modulation Types - Custom Digital Mod
The available predefined modulation types are ASK (amplitude shift keying), FSK (fre-
quency shift keying), PSK (phase shift keying) and QAM (quadrature amplitude modu-
lation). Additionally, a user defined modulation mapping can be applied (see chap-
ter 5.8.3.2.1, "User Mapping", on page 341).
The actual modulation procedure is described by mapping, which assigns I and Q values
(PSK and QAM) or frequency shifts (FSK) to every modulation symbol that occurs. This
is represented graphically in the constellation diagrams.
The mapping for the selected modulation type is displayed in the "More..." submenu in
the "Modulation" menu section (see "More - Modulation Type - Digital Modulation"
on page 355).
The QAM procedures 16QAM, 32QAM, 64QAM have been produced in accordance with
ETSI standard ETS 300429 for digital video broadcasting (DVB). The QAM procedures
256QAM and 1024QAM are not specified in this standard, but have been produced
according to the same basic principles.
In the case of all FSK procedures, the user can set the symbol rate fSYMB up to a max-
imum value (see data sheet). If MSK is selected, the frequency deviation (FSK deviation)
cannot be set since it is permanently set to ¼ of the symbol rate.
Baseband Signal - Baseband Block
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