Source Power Linearity Test - Keysight N5227A Service Manual

PNA Series Microwave Network Analyzers
N5227A

Source Power Linearity Test

Function of the Test: To verify that the power level is linear over the analyzer's frequency range and to check
the linearity of the automatic leveling control (ALC).
Specification Tested: Power Sweep Range and Power Level Linearity
Equipment Used:
• Test cable
• 20 dB attenuator if the analyzer does not have an internal step attenuator
Description of the Test:
Ports 1 and 2 are tested as a pair. The Port 2 receiver is used to test the linearity of the source power out of
Port 1, and vice versa. Ports 3 and 4 are similarly tested as a pair on 4-Port analyzers. The receiver linearity is
the standard 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 port pair to be measured.
3. A test cable is connected between the port pair to be tested with 20 dB of attenuation in series with the
cable. This is done with an internal source step attenuator or an external 20 dB attenuator. This
attenuation ensures that 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 maximum ALC power setting range in 1 dB
steps, and the receiver power is measured at each setting.
6. The non-linearity in dB at each frequency point is calculated as the difference between the change in the
source power setting away from Preset and the change in the receiver power reading.
7. This power linearity measurement is repeated at several CW frequencies across the full frequency range
of the analyzer.
If the Analyzer Fails this Test:
• Perform the "Source Adjustment" on page 3-42
• If the analyzer still fails this test, troubleshoot the source section of the analyzer and then repeat this
test. Refer to "Checking the Source Group" on page
Service Guide N5227-90001
and repeat this test.
4-30.
Tests and Adjustments
Performance Tests
3-31