Rohde & Schwarz FSP3 Service Manual page 191

R&S FSP
Testing the Signal Paths
Overview of the test sequence
• The internal source for the test signal (CAL signal) has already been tested with testing the reference
signals.
• Testing all attenuators.
• Testing the output level of the standard frontend using a level detector at the IF-filter input.
• Testing all signal paths inside the IF filter.
• Testing all (digital) signal paths and the signal processing incl. RAM on the detector board.
Normal action
Signal Path via RF Attenuator
It is assumed that the signal path is continuous;
an absolute level error of up to 20 dB is permitted.
The attenuators are measured in relation to the
calibration source, by switching over the latter
between 0 dBm and -30 dBm. The 10-dB, 20-dB,
40-dB attenuators are checked to ±3 dB.
RF-Att CAL level
0 -30
30 0
10 -30
40 0
1164.4556.82
Tested attenuator
Reference measurement
10 dB + 20 dB
Reference measurement
40 dB
3.87
Error and error cause
If there is no measured value in the ±20-dB
range, the error is likely to be located in the
subsequent signal path. The test does not
reveal any information on the RF attenuator.
The selftest is continued.
FATAL ERROR!
RF-Attenuator FAIL.
Selftest aborted.
If individual measurements, only, violate the
tolerances, the RF attenuator is clearly faulty:
error message
Important: Since a faulty RF attenuator causes
many subsequent errors to occur with
the IF-filter test, proper functioning of
the attenuator is a must.
Troubleshooting
E-1