HP 11848A Service Manual page 32

General Information Model 11848A
The complete calibration for a HP 3048A Phase Noise Measurement System includes the following:
1. HP 3561A Dynamic Signal Analyzer bench calibration.
2. RF Analyzer bench calibration. (If an RF analyzer is configured in the system.)
3. HP 3048A Rinctional Checks.
4. HP 11848A Adjustments. (The adjustments should only be run if the Functional Checks show a
problem.)
5. HP 3048A System Calibration Option 2. (This is total calibration of the HP 11848A Interface's
measurement paths.)
6. HP 3048A Performance Tests.
Before calibrating the System, the HP 3561A Dynamic Signal Analyzer and any configured RF analyzer
should be separately bench calibrated if they are beyond their calibration period.
NOTE
Measurement of phase noise is a ratio measurement where both the
numerator (the noise power) and the denominator (the carrier's power)
of the ratio are measured by the same system spectrum analyzer(s). The
accuracy of this relative measurement depends on the amplitude linearity
of the spectrum analyzer. A precision attenuator is used, in turn, to verify
the linearity specification of the spectrum analyzer. The amplitude linearity
calibration of the spectrum analyzer will be traceable to the National Bureau
of Standards (NBS) if the precision attenuator and other instrumentation
used to perform the calibration is traceable to NBS.
The following are guidelines as to when the Interface hardware calibration and System performance
tests should be run:
• It is not necessary to calibrate the Interface after the System is initially installed. The calibration
procedure is done at the factory before shipment, and the unique calibration data for the Interface
is stored on a software disc. This disc is included within the software set shipped with your
Interface.
• Whenever the environment changes 10° C or more, Option 1 calibration should be run to generate
new calibration data for the Interface to ensure accurate System performance.
• Once a year, after a repair of the Interface, or when a problem is suspected in the Interface the
following test should be run to ensure accurate System measurement results:
a. Functional Checks.
b. Adjustments. (The adjustments should only be run if the Functional Checks show a problem.)
c. Calibration Option 2. (This is a total calibration of the Interface measurement paths.)
d. Performance Tests.
The performance tests can be run more often if desired to ensure that the system meets the published
specifications contained in Section 1 of the HP 3048A Operating Manual.
It is suggested that the performance test be run in the following order:
1. Spur Accuracy Performance Test (spurious signal).
2. Noise Flatness Performance Test. (This test need only be run if an RF analyzer is included in
the system configuration.)
3. Noise Floor Performance Test.
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