The Spectrum Application (RF Measurements)
R&S
®
FPL1000
287
User Manual 1178.3370.02 ─ 09
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. Correction is done by subtracting the reference trace from the measure-
ment results. The resulting level values are provided in dB. This process is referred to
as
normalization
. Normalization is automatically enabled after calibration, but it can be
enabled or disabled as required. If normalization is enabled, "NOR" is displayed in the
channel bar, next to the indication that a tracking generator is being used ("Trk.Gen").
The normalized 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
If any of the calibration measurement settings are changed, the stored reference trace
is no longer 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. Approximate normalization is indicated
by the "APX" label in the channel bar (instead of "NOR").
Approximate normalization occurs if one or more of the following values deviate from
the calibration settings:
●
Coupling (RBW, VBW, SWT)
●
Reference level, RF attenuation
●
Start or stop frequency
●
Output level of internal generator
●
Detector (max. peak, min. peak, sample, etc.)
●
Frequency deviation at a maximum of 201 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-
tion of the intermediate values is applied. If the span increases, the values at the left or
right border of the reference dataset are extrapolated to the current start or stop fre-
quency, i.e. the reference dataset is extended by constant values.
Thus, the instrument settings can be changed in a wide area without giving up normali-
zation. This reduces the necessity to carry out a new normalization to a minimum.
The normalized trace in the display
The normalized reference trace is also displayed in the spectrum diagram, by default at
the top of the diagram (90% of the window height). It is indicated by a red line labeled
"NOR", followed by the current reference value. However, it can be shifted vertically to
Receiving Data Input and Providing Data Output
