Agilent Technologies N5242A, Service Manual

Page: 64 / 342

3-32 Service Guide N5242-90001
Tests and Adjustments PNA Series Microwave Network Analyzers
Performance Tests N5242A
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: A power meter, power sensor, a calibration kit, and a test cable.
Description of the Test:
1. The analyzer is set to various CW frequencies across its frequency range at an IF
bandwidth of 1 kHz and 801 points per sweep.
2. A test cable is connected to the driving port for the measurement and a power sensor is
connected to the other end of the cable.
3. The power level at the end of the cable is set to
−
5.00 dBm.
4. The power sensor is disconnected and the cable is connected to the port to be tested.
5. The absolute power level in dBm (log magnitude) is read: ( P
log
).
6. The test cable is removed and loads are connected to both ports.
7. The analyzer’s trace is set to represent the absolute power level (linear magnitude) for
the receiver under test and a sweep is taken.
8. The mean of the points on the trace, in watts, is read: ( P
lin
).
9. Average power in dBm is calculated: P
dBm
=
10
∗
Log10(P
lin
∗
1000) .
10. Corrected noise floor in dBm for a 10 Hz IF bandwidth = P
dBm
−
19.96 dB
−
(5.00-P
log
) .
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
“Removing and Replacing the A23 and A24 Mixer Bricks” on page 7-34 .
• 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 7-14 .