R&S AFQ100A
AFQ Commands - Signal Generation
1401.3084.32 6.21
E-3
{LEVEL OFFSET: RMSOffset_dB,PeakOffset_dB} (optional for waveforms)
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.
RMSOffset_dB
'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 3dB 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 = |SIQ|max = sqrt(I2+Q2)max = 0 dB)
PeakOffset_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 in the majority of cases 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 = |SIQ|max =
sqrt(I2+Q2)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 follows:
crest factor = |PeakOffset_dB - RMSOffset_dB|
Example:
{LEVEL OFFSET: 3.45,2}
IEC bus query:
"WAV:TAG? 'LEVEL OFFSET'"
'queries the content of the
'LEVEL OFFSET'
tag of the selected waveform
file.
Response:
"'3.45,2'"
'the level of the waveform is below full scale, clipping will not occur.
{SAMPLES: Samples} (optional for waveforms)
The tag contains the number of I/Q samples in the waveform in ASCII format.
Example:
{SAMPLES: 4333}
IEC bus query:
"WAV:TAG? 'SAMPLES'"
'queries the content of the 'SAMPLES' tag of the selected waveform file.
Response:
"'4333'"
'the waveform contains 4333 I/Q samples.
