Agilent Technologies E4440A, Service Manual

Page: 98 / 436

98 Chapter 4
Troubleshooting the RF Section (E4446A, E4447A, E4448A)
RF Section Description (E4446A, E4447A, E4448A)
A21 FELOMA and A29 FELOMA/SBTX Driver
Figure 4-6 FELOMA Block Diagram
The A21 FELOMA (Frequency Extended LO Multiplier-Amplifier)
provides amplitude leveling and distribution of the LO signal from the
A18 YTO assembly. For frequency bands 0, 1, 2, 3 and 4, the 3 to 7 GHz
LO is distributed to the Lowband or the RYTHM, to the 1
st
LO Out
port, and to the A12 LO Synthesizer assembly. In frequency bands 5
and 6, the LO frequency is doubled and filtered before being sent to the
SBTX.
The amplitude leveling of the 3 to 7 GHz LO signal inside FELOMA,
biasing, and LO port switching is controlled by the A29 SBTX driver
assembly.
Some common failure symptoms of a faulty FELOMA or the SBTX
driver includes YTO unlocks, increased residual responses, LO
unleveled errors, and low signal amplitude in one or more frequency
bands. The troubleshooting process below will help you determine
which of the two assemblies is faulty.