HP 8360 B Series User Manual page 215

User Flatness Correction Table as Displayed by the Swept Signal Generator
Theory of operation
The unparalleled leveled output power accuracy and flatness of the
HP 8360 B-Series swept signal generator. This is achieved by using a
new digital (versus analog) design to control the internal automatic
leveling circuitry (ALC).
An internal detector samples the output power to provide a dc
feedback voltage. This voltage is compared to a reference voltage
which is proportional to the power level chosen by the user. When
there is a discrepancy between voltages, the power is increased
or decreased until the desired output level is achieved. For
comprehensive theory on the ALC system, refer to the IALC) entry in
the "A" section of this manual.
The factory-generated internal calibration data of the swept signal
generator is digitally segmented into 1601 data points across the
start/stop frequency span chosen. Subsequently, these points are
converted into 1601 reference voltages for the ALC system. The
digital ALC control scheme not only delivers excellent power
accuracy and flatness at the output port of the swept signal
generator, but also provides the means to execute the user flatness
correction feature.
Generally, a power meter is required to create a table of correction
data that produces flat power at the test port. You may measure
and enter correction data for up to 801 points. The correction data
contained in the table is linearly interpolated to produce a 1601-point
data array across the start/stop frequency span set on the swept
signal generator. The 1601-point data array is summed with the
internal calibration data of the swept signal generator (Figure F-3).
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Figure F-2.
Operating and Programming Reference F-7
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