262 Keysight N9010A EXA Service Guide
Analog/Digital IF Troubleshooting
25 MHz BW IF Section
A2 Analog I.F. Assembly Theory of Operation
Input Switch and Filter
A 322.5 MHz input signal is received from the A13 RF Front End Assembly.
For analyzers equipped with Option CR3 and/or CRP, the 322.5 MHz input
signal is routed from the A13 Front End Assembly to the IF MUX on the A15
Front End Control Assembly and from there to the A2 Analog IF Assembly.
The signal then goes through a band pass filter centered at 322.5 MHz with
a 25 MHz bandwidth. A cal comb signal can be automatically switched in at
the input of the assembly to calibrate the prefilters.
Step Attenuator and Amplifier
A 1 dB step attenuator follows to compensate for band gain differences.
The signal then goes through a high-dynamic range amplifier.
Image Filters
One of three different filter paths will be selected automatically, depending
on the analyzer mode.
•The through path is selected in IQ Analyzer Mode and wide-band
demod.
•The 12 MHz ceramic bandpass filter is used for normal Signal Analyzer
swept and FFT operation.
•The 300 kHz Surface Acoustic Wave (SAW) is used for ACP modes.
Mixer
There are two mixers that reside on this assembly. The first mixer is used to
down convert the 322.5 MHz input to the final 22.5 MHz I.F. The other mixer
is described in the I.F. Comb Cal section.
3rd LO
The 300 MHz 3rd L.O. signal comes from the A16 Reference Assembly and
conditions it for use as an L.O. in the two mixers that reside on this
assembly. The third L.O. power is ~ +10 dBm to optimize the conversion
efficiency of the first mixer.
I.F. Comb Cal
The 2nd mixer is used to mix the 300 MHz L.O. from the Reference
Assembly with the 22.5 MHz cal comb signal from the A3 Digital I.F. to
allow calibration of the prefilters and overall passband phase and
amplitude. The signal is attenuated by 20 dB if necessary. A limiter is used
to reduce amplitude variation effects.
Refer to Chapter 12, “Block Diagrams.”.
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