
When the system measures the calibration spur, the analyzer does a
peak search over a frequency span of two times the entered spur offset
frequency. Once the spur has been located, the level of the spur is
measured and used to calculate the Detector Constant.
Considerations for the Derive From Double Sided
Spur Method
Requires an RF Spectrum Analyzer or modulation analyzer capable of
measuring the carrier frequency and the modulation sidebands unless a
calibrated AM source is being used.
For optimum results, an input power level of +10 dBm is recommended
for the HP 33330C LBSD AM Detector.
Unequal sidebands on the carrier potentially indicate a $M component
is present. If the sidebands are greater than 2 dB a different calibration
source should be used. Variations greater than 2 dB can effect the certainty
of the Detector Constant.
When under system control, the calibration source is set for an output
level of +10 dBm. If this level setting is not possible on the source you
are using, return to the Source Control menu and select manual control
for the calibration source. This will allow you to control the source level
output.
The amplitude value entered in the Calibration Process display is used
to derive the percentage of modulation at which to set the calibration
source. If the calibration source does not provide the necessary resolution
for setting the exact percentage derived from the entered amplitude, the
Detector Constant will be in error. It is therefore recommended that
—40 dBc be entered as the amplitude; this value corresponds to a two
percent modulation which is available in all of the supported RF Sources.
2-96 Calibr Process: AM Noise
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