85 Mhz Bw If Section; A25 Wideband Analog If Assembly Description; A25 Wideband Analog If Assembly Theory Of Operation - Keysight n9020a Service Manual

Analog/Digital IF Troubleshooting

≥ 85 MHz BW IF Section

≥ 85 MHz BW IF Section

A25 Wideband Analog IF Assembly Description

The analyzer's RF input signal is down converted to a 300 MHz intermediate
frequency by the A13 Front End assembly and routed through the A15 Front
End controller to A15J901. Cable W53 connects A15J901 to the input of the
A25 Wideband Analog IF at J101. The signal is filtered, attenuation and gain
applied based upon the instrument settings. This signal is then sampled by the
ADC and the resultant data is the sent to the A26 Wideband Digital IF for
processing via the J2 ribbon cable. The A26 Wideband Digital IF has no service
accessible locations and should be troubleshot from the front panel controls.
Inputs to the A25 Assembly
Outputs from the A25 Assembly

A25 Wideband Analog IF Assembly Theory of Operation

The A25 Wideband Analog IF assembly primary role is to properly filter and
apply attenuation or gain to optimize the level going to the ADC and provide
sufficient pre-filtering to reject images that would otherwise interfere with the
signal of interest. Precision alignments are used to calibrate the filters,
attenuators and gain of this assembly. It is not uncommon that the reported
failure will come from failures reported when an alignment fails for this
assembly. The alignment history file is a good indicator of a failure for this
assembly. This file is a text file that can be edited with Notepad. The file is
located in the following location:
E:\AlignDataStore\AlignmentHistory.txt
This file will list all alignments that have passed or failed. Alignments reporting
a failure of the WBAIF assembly can in many cases be attributed to failure of
this assembly. If however these errors follow errors in the RF section of the
instrument, it is possible that additional WBAIF error will appear due to
missing RF Calibration signals and not related to the A25 Wideband IF
assembly.
A25J101 300 MHz IF signal (from A15J901 Front End Controller)
A25J301 2400 MHz reference from A16 Reference Assembly via W34 cable
A25J805 Step Calibrator from A3J17 40 MHz Digital IF via W45 cable
A25J302 2400 MHz Reference Out
A25J102 300 MHz IF Out to A3J15 of the 40 MHz Digital IF
A25J806 50 MHz Comb Out to A16 Reference assembly A16J726 via W56
cable
A25J2 ADC Data to 140 MHz Digital IF A26J504 via W44 cable
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