Configuring the internal baseband source
R&S
®
SMM100A
183
User Manual 1179.1341.02 ─ 05
The tag determines the level of the ARB signal in the waveform file. The offset levels
define the offset of RMS and peak value relative to the 16-bit full scale modulation
(-32767 to + 32767) = 0 dB.
Setting parameters:
RMSOffset_dB
Defines the RMS level offset of the signal relative to full scale
ARB signal in the
WAVEFORM
tag. The offset is defined in ASCII
float format. The value is always positive.
A 3 dB value indicates that the RMS level of the signal is 3 dBs
below the full scale.
full scale = max. amplitude of vector of I/Q samples = |S
IQ
|max =
sqrt(I
2
+Q
2
)max = 0 dB
PeakOffset_dB
Defines the peak level offset of the signal relative to full scale for
the ARB signal in the
WAVEFORM
tag. The offset is defined in
ASCII float format.
The value usually equals 0 dB as usually the I/Q samples
(signed 16-bit integer values) are modulated to full scale: Full
scale = 0 dB = max. amplitude of vector of I/Q samples = |S
IQ
|
max = sqrt(I
2
+Q
2
)max = (2
15
)-1 = 32767.
A positive
PeakOffset_dB
value indicates that a headroom to
full scale is provided when generating the waveform. A negative
PeakOffset_dB value indicates that overrange is likely for some
samples, i.e. clipping might occur.
The crest factor can be calculated from the two values as fol-
lows:
Crest Factor = |PeakOffset_dB - RMSOffset_dB|
Example:
{LEVEL OFFS: 3.45,2}
BB:ARB:WAV:TAG? 'LEVEL OFFS'
Queries the content of the
LEVEL OFFS
tag of the selected
waveform file.
Response: 3.45,2
The level of the waveform is below full scale, clipping does not
occur.
Usage:
Setting only
{MARKER MODE [#]: GENERATOR}
(Optional for waveforms)
The tag defines how the marker signals are generated. The tag is included in the
waveforms, created by the R&S
WinIQSIM2 software.
●
Tag not used
The marker signals defined with the tag
rate binary control list. When the waveform is loaded into the ARB, this control list
is also loaded automatically and processed synchronous with the waveform.
Note:
This method reduces the maximum waveform length (given as number of
samples). The number of available samples is limited, because each marker
Using the arbitrary waveform generator (ARB)