Configuring the internal baseband source
R&S
®
SMM100A
152
User Manual 1179.1341.02 ─ 05
4.6.2.4
Impact of enabled number of marker signals on waveform length
The R&S
SMM100A provides the possibility to define marker signals, that are sent to
the marker outputs in synchronicity with the I/Q output signals. Marker signals can be
either predefined or later defined.
The I/Q data and marker data are located in separate memory areas of the SDRAM
and can be independently configured. Each marker signal requires 1 bit of the availa-
ble memory size. Sometimes, it is useful to generate a modulation signal without extra
marker signals to increase the maximum waveform length.
The following example explains the dependency between the number of enabled
marker signals, the available memory size, and the resulting waveform length.
Example: Calculating the maximum waveform length
The calculation in this example assumes R&S
SMM100A equipped with option
R&S
SMM-K511 (512 Msamples).
●
Total memory size = 512 MB
●
Required memory size (per complex sample) = 32 bits + 4 bits = 36 bits = 4.5
bytes, where:
–
The raw I/Q samples are saved as 16-bit values;
That is, for I/Q data = 2 x 16 bits = 32 bits (16 bits per I/Q channel)
–
Each software defined marker requires 1 bit;
That is, for 4 enabled markers = 4 x 1 bit = 4 bits
●
Maximum waveform length (with 3 markers) = 512 MB / 4.5 bytes = 113
Msamples
●
Theoretical maximum waveform length (no markers) = 512 MB / 4 bytes
= 128
Msamples
Hence, a memory size of 512 MB yields a maximum waveform length of 116
Msam-
ples, if three markers are enabled. The maximum waveform length increases to
128
Msamples, if the internal hardware markers are used, and the complete memory is
available for I/Q data.
The minimum length of a waveform is 512 samples. A waveform shorter than this value
is automatically repeated until it reaches the minimum length.
4.6.3
ARB settings
Access:
► Select "Baseband > ARB".
The "ARB" dialog enables direct selection of the waveform file to be processed, the
selection of a test signal or access to the multi-segment and multi-carrier settings.
The remote commands required to define these settings are described in
ter 13.16.4.3, "SOURce:BB:ARBitrary subsystem"
Using the arbitrary waveform generator (ARB)
