Keysight N5221A/22A Service Guide 3-33Tests and AdjustmentsPerformance TestsTroubleshoot the source section of the analyzer and then repeat this test. Referto “Checking the Source Group” on page 4-34.Source Power Linearity TestFunction of the Test: To verify that the power level is linear over the analyzer’sfrequency range and to check the linearity of the automatic leveling control(ALC).Specification Tested: Power Sweep Range and Power Level LinearityEquipment Used:— Test cable— 20 dB attenuator if the analyzer does not have an internal step attenuatorDescription of the Test:Ports 1 and 2 are tested as a pair. The Port 2 receiver is used to test thelinearity of the source power out of Port 1, and vice versa. Ports 3 and 4 aresimilarly tested as a pair on 4-Port analyzers. The receiver linearity is thestandard against which the source linearity is checked.1. The analyzer is Preset.2. The analyzer is set up for a CW transmission measurement on the test portpair to be measured.3. A test cable is connected between the port pair to be tested with 20 dB ofattenuation in series with the cable. This is done with an internal sourcestep attenuator or an external 20 dB attenuator. This attenuation ensuresthat the receiver remains in its linear range.4. The receiver measurement is normalized at this Preset power level.5. The source setting is then stepped from the minimum to the maximumALC power setting range in 1 dB steps, and the receiver power ismeasured at each setting.6. The non-linearity in dB at each frequency point is calculated as thedifference between the change in the source power setting away fromPreset and the change in the receiver power reading.7. This power linearity measurement is repeated at several CW frequenciesacross the full frequency range of the analyzer.If the Analyzer Fails this Test:— Perform the “Source Adjustment” on page 3-42 and repeat this test.— If the analyzer still fails this test, troubleshoot the source section of theanalyzer and then repeat this test. Refer to “Checking the Source Group” onpage 4-34.
