Trace Noise Test - Keysight N5241A 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 S21 and S12 measurements. Ports 3
and 4 are similarly tested as a pair on 4-port analyzers using S43 and S34
measurements.
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
Replacing the A4–A13 Boards (For analyzers with serial numbers prefixed
MY/SG/US5150 and below.)" on page 7-14
the A4–A13 Boards (For analyzers with serial numbers prefixed
MY/SG/US5201 and above.)" on page
— If the analyzer still fails this test, replace the mixer module for the failing
receiver, and then repeat this test.
3-36
"Removing and
"Removing and Replacing
and
7-17.
Keysight N5241A/42A/49A Service Guide