Configuring the Internal Baseband Source
R&S
®
SMW200A
246User Manual 1175.6632.02 ─ 30
bol. The resulting modulated signal is graphically represented by a constellation dia-
gram, in that each possible symbol is represented by a discrete point on a complex
plane. The number of used bits per symbol is a modulation parameter. The exact posi-
tion of the symbols on the constellation diagram is determined by the used coding
scheme. You can also change the symbol position by applying 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.
For 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 modulation is perma-
nently set to ¼ of the symbol rate. Also a variable FSK modulation with definable devi-
ation per symbol is available and for even greater flexibility. A user-defined modulation
mapping can be applied, see "User mapping" on page 246.
User mapping
A user-defined modulation-mapping file can also be selected as modulation-mapping
source. Valid files have the extension *.vam and can be created 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).
The main purpose of "mapwiz" is the assignment of logical symbol numbers to constel-
lation points and the selection of modulation-specific parameters. Also, the tool sup-
ports the creation of nearly any arbitrarily chosen constellation diagram. The output of
"mapwiz" is a mapping file (*.vam) that can be imported into a R&S SMW. The pro-
gram was developed on a 32-bit Microsoft Windows platform under MATLAB.
For more information, see "Introduction to "mapwiz" Mapping Editor" at the
Rohde & Schwarz webpage.
The remote commands required to define the modulation settings are described in
Chapter 14.19.4.2, "SOURce:BB:DM Subsystem", on page 988.
Related settings:
●
Chapter 5.6.3.4, "Modulation Settings", on page 271
5.5.1.5 Supported Coding Schemes
Coding is a technique used to improve the signal properties and signal reception and is
required only when using some types of modulation. In general, the coding schemes
are applied before modulation. The modulation symbols are coded directly before I and
Q values or frequency shifts are assigned. The applied coding is directly related to the
selected modulation methods. The relation implies that coding schemes are not freely
combinable with the modulation methods.
Refer to Chapter 5.6.5.1, "Common Coding Algorithms", on page 291 for overview on
the available coding combinations. This section also defines the modulation types for
which the various coding procedures can be used.
Common Functions and Settings in the Baseband Domain
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