Keysight N5224A/25A Service Guide 3-37Tests and AdjustmentsPerformance Tests— If the analyzer still fails this test, replace the A23 mixer brick for a Port 1 orPort 2 failure or the A24 mixer brick for a Port 3 or Port 4 failure, then repeatthis test. Refer to “Removing and Replacing the A27 and A28 Mixer Bricks”on page 7-36.Noise Floor TestFunction of the Test: To measure the absolute power level of the noise floor forthe analyzer’s receivers.Specification Tested: Test Port Input–Test Port Noise FloorEquipment Used:— Power meter— Power sensors— Test cable— Calibration kitDescription of the Test:This test uses the source signal out of one analyzer test port as part of thenoise floor measurement on another test port. Port 2 is the source port whenmeasuring the noise floor of Port 1. Port 1 is the source port when measuringthe 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 thesource port and the test port to be measured. The analyzer is set to an IFbandwidth 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 anynecessary adapters.5. For hundreds of frequencies across the analyzer’s full range, a sourcepower calibration is performed to ensure a flat power response at the endof the cable at the Preset power level.6. The power sensor is disconnected and the cable is connected to the portto be tested.7. A CW linear measurement sweep is measured for each test point. Thereceiver reference power level, Pref, in dBm is calculated for each pointfrom the mean of each sweep.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. Thereceiver test power level, Ptest, in dBm is calculated for each point fromthe mean of each sweep.
