56 Chapter 2
Installation and Setup
Calibrating System Components
To recall one set of cal factors at one frequency:
1. Press
File, Load, Type, State, and find the file name you want to load.
2. Press
Load Now.
See “Store and Recall TRFL Cal Factors” on page 190 for information on how to
save remotely.
PSA Range Calibration
Only the Tuned RF Level measurements require the PSA range calibration.
As the signal level into the PSA is decreased, the signal to noise ratio changes not
only because the signal is closer to the noise but because some of the internal
settings of the PSA change to optimize the measurement. The measuring routine in
the PSA calculates the approximate power level a range calibration is needed
based on S/N. When the signal level at the PSA reaches this range calibration
power, the calibration routine makes measurements in both the current range and
the next range. A Cal Factor value is generated and is used to correct the
measurement.
There are two range calibrations; Range 1 to Range 2 and Range 2 to Range 3.
The range calibration procedure can be a separate process that you perform before
you begin the TRFL measurement on your UUT (the process outlined here), or the
range calibration can be performed during the TRFL measurement of the UUT.
The range calibration can be triggered automatically by the PSA, or it can be
triggered manually. Press
Meas Setup, Range Switching, to select Auto or Man.
Auto mode will probably be used most of the time. In Man mode, a Recal message
appears on screen alerting the user a range calibration is required. The range
calibration will be held off until you press
TRFL Calibrate. There may be
situations slightly above the calculated range switch point where you want to
continue making measurements in the current range.
NOTE The range calibration “assumes” the power level of the current range is close to the
range switch point. Example: if the PSA calculates the range 2 to range 3 switch
point at − 80 dBm, the range calibration must be done within a few dB of − 80
dBm. Therefore, it is important to step the power level down in steps of 10 dB or
less to allow optimum calibration.
If you chose to allow the range calibration to occur as part of the TRFL
measurement of the UUT, the UUT measurement will be interrupted while the
calibration takes place.
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