Noise Floor Test - Keysight N5221A Service Manual

PNA Series Microwave Network Analyzers
N5221A/22A

Noise Floor Test

Function of the Test: To measure the absolute power level of the noise floor for the analyzer's receivers.
Specification Tested: Test Port Input–Test Port Noise Floor
Equipment Used:
• Power meter
• Power sensors
• Test cable
• Calibration kit
Description of the Test:
This test uses the source signal out of one analyzer test port as part of the noise floor measurement on
another test port. Port 2 is the source port when measuring the noise floor of Port 1. Port 1 is the source port
when measuring the noise floor of Ports 2, 3, and 4.
1. The analyzer is Preset.
2. The analyzer is set up for a CW transmission measurement between the source port and the test port to
be measured. The analyzer is set to an IF bandwidth of 1 kHz and 801 points per sweep.
3. A test cable is connected to the source port.
4. A power sensor is connected to the end of the test cable with any necessary adapters.
5. For hundreds of frequencies across the analyzer's full range, a source power calibration is performed to
ensure a flat power response at the end of the cable at the Preset power level.
6. The power sensor is disconnected and the cable is connected to the port to be tested.
7. A CW linear measurement sweep is measured for each test point. The receiver reference power level,
P , in dBm is calculated for each point from the mean of each sweep.
ref
8. The test cable is removed and loads are connected to both ports.
9. A CW linear measurement sweep is measured for each test point. The receiver test power level, P
dBm is calculated for each point from the mean of each sweep.
10. The corrected noise floor in dBm is calculated for a 10 Hz IF bandwidth using: P
dB – (Preset Power – P
If the Analyzer Fails this Test:
• If the analyzer fails this test, replace the A23 mixer brick for a Port 1 or Port 2 failure or the A24 mixer
brick for a Port 3 or Port 4 failure, then repeat this test. Refer to
A24 Mixer Bricks" on page
• If the analyzer still fails this test, replace the A12 SPAM board and then repeat this test. Refer to
"Removing and Replacing the A4–A13 Boards" on page
Service Guide N5222-90001
).
ref
7-34.
NoiseFloor
"Removing and Replacing the A23 and
7-14.
Tests and Adjustments
Performance Tests
, in
test
= P – 19.96
test
3-37