Trace Noise Test - Keysight N5221A Service Manual

Tests and Adjustments
Performance Tests

Trace Noise Test

Function of the Test: To measure the stability of a signal in the internal source and receiver system of your
analyzer.
Specification Tested: Test Port Input–Trace Noise Magnitude and Trace Noise Phase
Equipment Used: A test cable.
Description of the Test:
Trace Noise is a calculation of the standard deviation of a 201 point CW measurement. In a healthy analyzer,
this measurement is only affected by the sampling error of the analog to digital converters on the SPAM
board.
Ports 1 and 2 are tested as a pair using S
pair on 4-port analyzers using S
1. The analyzer is Preset.
2. The analyzer is set up for a 201 point CW transmission measurement for the port pair to be tested with
the specified IF bandwidth (typically 1 kHz). Both a magnitude and a phase trace are displayed.
3. A test cable is connected between the port pair to be tested.
4. The analyzer is set to a series of CW frequencies across its full frequency range. The analyzer's trace
statistics function is used to calculate the standard deviation of both the magnitude trace and the phase
trace.
5. These standard deviation values are reported as the analyzer's trace noise and are compared with the
Trace Noise magnitude and phase specifications.
If the Analyzer Fails this Test:
A failure of this test indicates a fault in the receiver's IF chain between the mixer and the A12 SPAM board.
This can indicate a faulty assembly or a loose cable.
• Check for proper torquing of all semi-rigid cables in the receiver chain, and then repeat this test.
• If the analyzer still fails this test, replace the A12 SPAM board and repeat this test. Most failures are due
to this board. Refer to
• If the analyzer still fails this test, replace the mixer module for the failing receiver, and then repeat this
test.
3-34
and S
21 12
and S measurements.
43 34
"Removing and Replacing the A4–A13 Boards" on page
PNA Series Microwave Network Analyzers
measurements. Ports 3 and 4 are similarly tested as a
N5221A/22A
7-14.
Service Guide N5222-90001