Keysight N9038A, Service Manual, Page: 297 / 745

Keysight N9038A MXE Service Guide 297
Front End Control
A15 Front End Control Assembly Troubleshooting
IF Switching
The A15 Enhanced Front End Control assembly has the ability to switch the IF
signal output from the A13 Front End Assembly to either the A2 Analog IF
assembly or the A3 Digital IF assembly. If an instrument has option B85
installed the signal will be routed to the A25 Wideband Analog IF assembly
instead of the A3 Digital IF, which will then route the signal to the A3 Digital IF
assembly when needed.
With the current configuration of the MXE there is no time other than during
the instrument internal alignments that the instrument uses the signal path to
the A3 Digital IF assembly. So this procedure will verify the correct signal
routing to the A2 Analog IF output, the A25 Wideband Analog IF output if
option B85 is installed, and the rear panel AUX IF output.
When the IF signal is routed to the A2 Analog IF assembly the frequency of the
signal is 322.5 MHz, when it is routed to the A3 Digital IF assembly it is 250
MHz, and when it is routed to the A25 Wideband Analog IF assembly it is 300
MHz. The instrument is able to vary the intermediate frequency by offsetting
the first local oscillator frequency accordingly.
A2 Analog IF Signal Routing
The 322.5 MHz IF signal routing for the A2 Analog IF output of the A15
Enhanced Front End Control board can be seen in the solid heavy blue line in
Figure 8-13 .
Figure 8-13 322.5 MHz IF Switching to A2 Analog IF