7
The following error messages may occur while
attempting to enable the flatness correction and/or
reducing the test port power level:
• If flatness correction is enabled before reducing
the test port power level, IF Overload or Source
1 Warning—RF Unleveled may be displayed on
the analyzer as the source becomes unleveled.
Unleveling occurs when the source attempts to
output its maximum specified power plus the
flatness correction.
• If the output power is reduced to a suitable test
port power level before turning flatness correc-
tion on, No IF Found may be displayed. There
may not be sufficient output power from the
source for the 8510C to phase lock to the signal.
These error messages should disappear when flat-
ness correction is enabled with the appropriate
test port power level setting. If the test port power
level is not correctly reduced, the source will
become unleveled and try to output maximum
power. Although flatness correction will be applied
to the unleveled signal, the measurement for the
unleveled portion of the frequency span will not be
valid because the flatness-correction feature can-
not compensate for the inconsistent power varia-
tions that occur.
Power control with flatness correction
The ability to compensate for power variations
across the entire measurement span of the source
will depend on the highest leveled output power
the source can produce and the amount of power
compensation required. The test port power may
be adjusted over the entire P
max
to P
min
range with-
out degrading the flatness-correction calibration.
Table 4 shows test port power ranges for various
source/test set combinations. To determine the test
port power levels for a particular frequency span,
choose a power level between P
max
of the highest
frequency in the measurement span and P
min
of the
lowest frequency in the measurement span. For
example, the power range for a 50 MHz to 20 GHz
span with an 83621B/8515A system is –13.5 dBm
to –26 dBm. A high-power Agilent 83623B adds
7 dBm to P
max
of the 83621B. If a user sets up a
50 MHz to 20 GHz measurement with an 83623B
and an 8515A, the test port power range is
–6.5 dBm to –26 dBm.
Operational Considerations
Calibration time
The user may choose to speed up the calibration process by reducing the number of trace points on the
analyzer. Table 5 provides some typical calibration times for flatness correction over the full frequency
span of the source for different source/test set combinations. Calibration times may be slightly reduced by
increasing the stepped measurement speed with the quick step feature on the Agilent 8510C.
Table 5. Typical calibration times (in minutes) versus number of calibration points with maximum leveled source power
Number of Points 83620B/83621B 83631B 83651B
with 8514B with 8515A with 8515A with 8517B
801 30 32 40 60
401 15 16 20 30
201 8 8 10 15
101 4 4 5 8
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