Keysight N9038A, Service Manual, Page: 220 / 745

220 Keysight N9038A MXE Service Guide
RF Downconverter Section
RF Downconverter Section Description
RF Section Signal Paths
Band 0 Signal Path - Input Frequencies
≤
3.6 GHz (Option 503, 508,
526, 544)
RF input frequencies
≤
3.6 GHz route through the low band path. Refer to
Chapter 15, “Block Diagrams.” for details.
The RF input signal entering the instrument by either of the two front panel
input connectors is routed through both of the instrument's input attenuators
(A9 & A10). The signal is then routed through the SW2 Transfer switch, where it
could either be directed through the RF Preselector section of the instrument
or bypass it. The output of the transfer switch is then routed to the A11 RF
Switch / High Band Preamp assembly where it is then directed to the A13 RF
Front End assembly.
There are two different signal paths at the band 0 input of the A13 RF Front
End assembly that the signal can be routed through, either through the low
band preamp and then to the low band 1st mixer, or around it and directly to
the mixer. The low band preamp has a gain of approximately 20 dB.
The RF input signal is then mixed with the 1st LO from the A14 LO Synthesizer
assembly to generate a 1st IF of 5122.5 MHz.
1st IF = RF + 1st LO = 5122.5 MHz
Since the RF input signal is < 3600 MHz for band 0, the RF input signal is
up-converted in the 1st mixer to the 1st IF. The 1st IF signal is then
down-converted using the 4800 MHz 2nd LO generated on the A16 Reference
assembly to generate a 2nd IF of 322.5 MHz.
2nd IF = 1st IF
−
2nd LO
2nd IF = 5122.5 MHz
−
4800 MHz = 322.5 MHz
The 322.5 MHz 2nd IF output exits the A13 RF Front End assembly at J7.
Refer to Chapter 15, “Block Diagrams.” .