Keysight E8357D/67D & E8663D PSG User’s Guide 319
Troubleshooting
RF Output Power Problems
CAUTION
If the power search reference has the incorrect RMS voltage, the output
power will be incorrect. Refer to
Figure 13-3, "Calculating the Output Power
Error for a Single Waveform Sample Point"
and
Figure 13-3
Calculating the Output Power Error for a Single Waveform Sample Point
Figure 13-4
Calculating the RMS Voltage of the Waveform
ARB RMS
During ARB RMS, the
Power Search Reference
is set to
ARB RMS, the I/Q modulation is disabled, and the I/Q
modulator is biased with a DC level that is equivalent
to the RMS voltage of the modulating signal. This
selection is typically used with internally generated
baseband I/Q modulations. When the search is
complete, the DC bias is removed and the I/Q signal is
reapplied to the I/Q modulator.
The RMS voltage value can be found in the waveform
header (Refer to
Chapter 3, “Basic Digital Operation.”
The RMS voltage value can be set by the user or
calculated by the signal generator.
NOTE
The ARB RMS softkey is only available when the internal Arb is enabled.
20
10
V
( )
1
(
)
V
( )
2
(
)
⁄
(
)
log
×
=
Where:
V1 is the actual waveform RMS voltage
V2 is the entered RMS voltage
The Output Power Error
Note: If the RMS voltage value entered is lower than the actual RMS voltage, the output power will be higher than desired.
If the RMS voltage value entered is higher than the actual RMS voltage, the output power will be lower than desired.
Because the RMS calculation, that is done by the signal generator, is slow
and may not be appropriate for your application, it is recommended that
the user calculate and enter in their measured RMS value for the
waveform file.
RMS value for the waveform =
SCPI Commands:
[:SOURce]:RADio:ARB:HEADER:RMS <"file_name">,<val>|UNSPecified
[:SOURce]:RADio:ARB:HEADER:RMS? <"file_name">
For a programming example of determining the RMS voltage of a waveform, refer to the Programming Guide and to the
Documentation CD that came with this instrument.
