Concepts and features
R&S
®
ZND
177
User Manual 1173.9557.02 ─ 61
calibration plane or to any other point in the test setup where the signal power is known
to be proportional to the power at the calibration plane.
By default, the source power calibration involves several steps:
1.
Reference receiver calibration:
The analyzer performs a first calibration sweep at
the source power that is likely to produce the target power ("Cal Power") at the cali-
bration plane. A known attenuation or gain at the source port and in the signal path
between the source port and the calibration plane can be specified:
The power which the external power meter measured at the calibration plane is
displayed in the calibration sweep diagram, together with the reference receiver
reading. The firmware uses the difference between the two traces to correct the
reference receiver reading.
2.
Internal source power flatness calibration:
In the following steps, the calibrated
reference receiver is used to adjust the source power. To this end, the R&S
ZND
performs a series of calibration sweeps at varying source power until the number of
"Total Readings" is reached or until the deviation between the calibrated reference
receiver power and the cal power is below a specified "Tolerance". The external
power meter is no longer used for these repeated calibration sweeps; everything is
based on the previously calibrated reference receiver. This speeds up the calibra-
tion procedure but does not impair its accuracy.
Tip:
Since version 3.0 of the analyzer firmware, it is also possible to perform the
source (flatness) calibration using a power meter (without previously calibrating the
reference receiver).
3. After the flatness calibration, the R&S
ZND performs an additional verification
sweep to demonstrate the accuracy of the calibration.
After the source power calibration, one can expect the power at the calibration plane to
be within the range of uncertainty of the power meter. The reference receiver reading
corresponds to the calibrated source power. After a change of the sweep points or
sweep range, the analyzer interpolates or extrapolates the calibration data; see
ter 4.5.6.3, "Power calibration labels"
4.5.6.2
Measurement receiver calibration
A measurement receiver calibration ensures that the power readings at a specified
receive port of the analyzer (b-waves) agree with the source power level calibrated at
an arbitrary calibration plane. Typically, the calibration plane is at the input of the
receiver so that the calibration eliminates frequency response errors in the calibrated
receiver.
In contrast, the reference receiver calibration ensures correct power readings for the
generated waves (a-waves).
Calibration
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