Keysight CXG, EXG, and MXG X-Series Signal Generators Service Guide 189
RF Assembly
A3 RF Assembly Overview
The Synthesizer section can also be frequency modulated by the FM output of
the Function Generator / Trigger Control section for the FM portion of option
UNT, AM, FM, Phase Modulation.
There are several adjustments related to the Synthesizer section found in the
performance verification and adjustment software for these instruments, which
will be covered later in this chapter.
There are several error messages that the instrument could display that relate
to this section. They are:
— 508 Synthesizer Unlocked
— 508 Synthesizer Unlocked; FracN Loop
— 508 Synthesizer Unlocked; Offset Loop (over)
— 508 Synthesizer Unlocked; Offset Loop (under)
— 508 Synthesizer Unlocked; Sum Loop (over)
— 508 Synthesizer Unlocked; Sum Loop (under)
If any of these is seen, see the “A3 RF Assembly Troubleshooting” section later
in this chapter.
Synthesizer Multiplier / Divider Section
The Synthesizer Multiplier / Divider section is the same for all versions of the
A3 RF assembly in all instruments.
The input to the Synthesizer Multiplier / Divider section comes from the output
of the Synthesizer section and has a range of 750 MHz to 1.5 GHz. There are
two outputs from this section, one that returns a 3 to 6 GHz signal to the
Synthesizer section as feedback for the phase lock loop of the synthesizer
output, and another that provides a 250 MHz to 6 GHz signal to the RF Output
section.
The 250 MHz to 6 GHz signal can also be routed to and from the A2 Vector
BBG assembly in vector instruments at J2004 and J2003 when digital
modulation is turned on. For microwave instruments a 2.5 to 5 GHz signal is
sent from J2004 to the A7A2 20 GHz Frequency Multiplier input on the A7
Micro-Deck assembly to generate output signals from 3.2 to 20 GHz.
As shown in Table 10-1, frequency multipliers and dividers are used to extend
the synthesizer frequency range to cover 250 MHz to 6 GHz.
Table 10-1 Synthesizer Multiplier / Divider Ranges
Input Frequency Multiplier / Divisor Output Frequency
1 GHz to 1.5 GHz ÷ 4 250 to 375 MHz
750 MHz to 1.5 GHz ÷ 2 375 to 750 MHz
750 MHz to 1.5 GHz X 1 750 MHz to 1.5 GHz
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