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Configuring the Internal Baseband Source
R&S
®
SMBV100B
104
User Manual 1178.4460.02 ─ 03
3.4.1.4
Supported Modulation Types
The R&S
SMBV100B supports a range of predefined digital and analog modulation
types. This section focuses on the possibility to digitally modulate the baseband signal.
The analog modulation methods provided for shifting the frequency bandwidth of the
RF signal are described in
Chapter 6.11, "Analog Modulations"
In the communication techniques, the commonly used digital modulation schemes are
based on keying. From the several existing keying techniques, this instrument supports
ASK (amplitude shift keying), FSK (frequency shift keying), PSK (phase shift keying),
and QAM (quadrature amplitude modulation). The digital modulation procedure is
described by mapping. That is, by the assignment of I and Q values (PSK and QAM) or
frequency shifts (FSK) to every modulation symbol. The resulting modulated signal is
graphically represented by a constellation diagram, in that each possible symbol is rep-
resented by a discrete point on a complex plane. The number of used bits per symbol
is a modulation parameter. The exact position of the symbols on the constellation dia-
gram is determined by the used coding and can be influenced by additionally applied
rotation.
Most of the provided modulation schemes are implemented according to a communica-
tion standard. The QAM procedures 16QAM, 32QAM, 64QAM for instance 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 stan-
dard, but have been produced according to the same basic principles.
In the case of all FSK procedures, you can set the symbol rate f
SYMB
up to a maximum
value (see data sheet). The frequency deviation (FSK deviation) of the MSK modula-
tion is permanently set to ¼ of the symbol rate.
In addition to the common modulation schemes, a variable FSK modulation with defin-
able deviation per symbol is available and for even greater flexibility, a user-defined
modulation mapping can be applied (see
User mapping
A user-defined modulation mapping file can also be selected as modulation mapping
source. The user modulation mapping file must have extension
*.vam
and can be cre-
ated with the Rohde
&
Schwarz software tool mapping wizard. The mapping wizard
(mapwiz) is a tool from Rohde
&
Schwarz designed for editing modulation schemes
(for example QPSK, 32QAM). Its main purpose is the assignment of logical symbol
numbers to constellation points and the selection of modulation-specific parameters.
Beyond this, it supports the creation of nearly any arbitrarily chosen constellation dia-
gram. The output of mapwiz is a mapping file (
*.vam
) that can be imported to a
R&S
SMBV100B. The program was developed on a 32-bit Microsoft Windows platform
under MATLAB. For more information, refer to the description "Introduction to "mapwiz"
Mapping Editor" at the Rohde
&
Schwarz webpage.
The remote commands required to define the modulation settings are described in
Chapter 12.16.4.2, "SOURce:BB:DM Subsystem"
Related settings:
●
Chapter 3.5.3.4, "Modulation Settings"
Common Functions and Settings in the Baseband Domain