Agilent Technologies 8590 Series Service Manual page 368

Assembly Descriptions and Block Diagrams
RF and LO Section for 8592L, 8593E, 8594E, 8594L, 8594Q, 8595E, and 8596E Analyzers
A9 Third Converter Assembly
The A9 Third Converter performs the following functions:
• Down-converts the 321.4 MHz IF to the final 21.4 MHz IF.
• Generates the 300 MHz third LO.
• Provides variable gain from the calibrator amplifier that adjusts the
amplitude of the 21.4 MHz IF during the analyzer
self-calibration routine.
• Generates the 600 MHz second LO drive signal for the A3A4 second
converter assembly and for the tracking generator (Option 010).
• Generates the 300 MHz CAL OUT signal at −20 dBm.
• Provides a buffered 300 MHz to drive the external reference PLL
circuitry on the A25 counterlock assembly.
Refer to Foldout 11-6 at the end of this chapter for details about the
operation of the A9 third converter assembly.
Refer to "Troubleshooting the A15 Motherboard Assembly"
Chapter 5 when tracing control signals for the A9 third converter
assembly.
The output of the 600 MHz surface acoustical wave (SAW) oscillator is
buffered, providing the second LO signal to the A3A4 second converter.
This signal is further buffered, divided by two, and buffered again to
produce three 300 MHz outputs. A second 600 MHz output drive signal
is available for the tracking generator (Option 010).
The amplitude of the 300 MHz signal from the calibrator amplifier is
adjusted to provide the −20 dBm output for the 300 MHz CAL OUT
signal. This amplifier produces rich harmonics that are used in the
analyzer self-calibration routines.
The 300 MHz signal sent to the 300 MHz Buffer produces the other two
300 MHz outputs:
• The 300 MHz third LO sent to the mixer/filter.
• The 300 MHz feedback signal sent to the A25 counterlock assembly
by the counterlock buffer. This signal is divided down and compared
to the 10 MHz reference in a phase/frequency detector on the A25
counterlock assembly. The output of the phase/frequency detector,
VTO_TUNE, is fed back to the 600 MHz SAW Oscillator to increase
its frequency stability.
The 321.4 MHz second IF signal from the A3A4 second converter is
amplified and bandpass-filtered on the A9 third converter assembly.
This signal is mixed with the 300 MHz third LO to produce the
21.4 MHz difference signal that is then bandpass-filtered and buffered.
368
CAL AMPTD
in
Chapter 9