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Calibration Considerations
Measurement Parameters
Calibration procedures are parameter-specific, rather than channel-specific When a parameter
is selected, the instrument checks the available calibration data, and uses the data found
for that parameter. For example, if a transmission response calibration is performed for
B/R, and an
S11
l-port calibration for A/R, the analyzer retains both calibration sets and
corrects whichever parameter is displayed.
Once
a calibration has been performed for a
specific parameter or input, measurements of that parameter remain calibrated in either
channel, as long as stimulus values are coupled. In the response and response and isolation
calibrations, the parameter must be selected before calibration: other correction procedures
select parameters automatically. Changing channels during a calibration procedure invalidates
the part of the procedure already performed.
Device Measurements
In calibration procedures that require measurement of several different devices, for example
a short, an open, and a load, the order in which the devices are measured is not critical.
,..
,..
Any standard can be re-measured, until the
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key is pressed. The change in trace during
measurement of a standard is normal.
Response and response and isolation calibrations require measurement of only one standard
device. If more than one device is measured, only the data for the last device is retained.
Omitting Isolation Calibration
Isolation calibration can be omitted for most measurements, except where high dynamic range
is a consideration. Use the following guidelines. When the measurement requires a dynamic
range of:
H
90
dB:
Omit isolation calibration for most measurements.
n
90 to 100
dB:
Isolation calibration is recommended with test port power greater than
0
dBm.
For this isolation calibration, averaging should be turned on with an averaging factor
at least four times the measurement averaging factor. For example, use use an averaging
factor of 16 for the isolation calibration, and then reduce the averaging factor to four for the
measurement after calibration.
n
100
dB:
Same as above, but alternate mode should be used. See page 5-53.
Saving Calibration Data
You should save the calibration data, either in the internal non-volatile memory or on a disk.
If you do not save it, it will be lost if you select another calibration procedure for the same
channel, or if you change stimulus values. Instrument preset, power on, and instrument state
recall
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also clear the calibration data.
6-72 Application and Operation Concepts