Common Measurement Settings
R&S
®
FSW
336
User Manual 1173.9411.02 ─ 19
The inherent frequency and power level distortions can be determined by connecting
the R&S
FSW to the signal generator. The R&S
FSW sends a predefined list of fre-
quencies to the signal generator (see also
The signal generator then sends a signal with the specified level at each frequency in
the predefined list. The R&S
FSW measures the signal and determines the level off-
sets to the expected values.
Saving calibration results
A reference dataset for the calibration results is stored internally as a table of value
pairs (frequency/level), one for each sweep point. The measured offsets can then be
used as calibration factors for subsequent measurement results.
The calibration can be performed using either transmission or reflection measure-
ments. The selected type of measurement used to determine the reference trace is
included in the reference dataset.
Normalization
Once the measurement setup has been calibrated and the reference trace is available,
subsequent measurement results can be corrected according to the calibration factors,
if necessary. This is done by subtracting the reference trace from the measurement
results. This process is referred to as
normalization
and can be activated or deactiva-
ted as required. If normalization is activated, "NOR" is displayed in the channel bar,
next to the indication that an external generator is being used ("Ext.Gen").The normal-
ized trace from the calibration sweep is a constant 0
dB line, as <calibration trace> -
<reference trace> = 0.
As long as the same settings are used for measurement as for calibration
, the normal-
ized measurement results should not contain any inherent frequency or power distor-
tions. Thus, the measured DUT values are very accurate.
Approximate normalization
As soon as any of the calibration measurement settings are changed, the stored refer-
ence trace will no longer be identical to the new measurement results. However, if the
measurement settings do not deviate too much, the measurement results can still be
normalized
approximately
using the stored reference trace. This is indicated by the
"APX" label in the channel bar (instead of "NOR").
This is the case if one or more of the following values deviate from the calibration set-
tings:
●
coupling (RBW, VBW, SWT)
●
reference level, RF attenuation
●
start or stop frequency
●
output level of external generator
●
detector (max. peak, min. peak, sample, etc.)
●
frequency deviation at a maximum of 1001 points within the set sweep limits (corre-
sponds to a doubling of the span)
Differences in level settings between the reference trace and the current instrument
settings are taken into account automatically. If the span is reduced, a linear interpola-
Data Input and Output
