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

51	2	2	2	4

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 Pmax to Pmin 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 Pmax of the highest frequency in the measurement span and Pmin 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 Pmax 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.