A14 Frequency Reference Board (S/N Prefixes <6021 Only); A23 Test Set Motherboard - Keysight N5224B Series Service Manual

Theory of Operation
Synthesized Source Group Operation
Together, these signal paths create the full output frequency range of 10 MHz
to 26.5 GHz that is sent to the A26 splitter (4-port only) where the signal is
divided and sent to the A27 and A28 (4-port only) mixer bricks as the LO
signal.
10 MHz REF INPUT (s/n prefixes
<6021 only)
10 MHz REF OUTPUT (s/n prefixes
<6021 only)
A14 Frequency Reference Board (S/N prefixes
This assembly provides stable reference frequencies to the rest of the
instrument. A high stability 10 MHz oven-controlled crystal oscillator (OCXO)
normally provides the frequency standard. However, if a 10 MHz external
reference signal is detected at the 10 MHz EXT REF IN port on the rear panel, it
is used as the frequency reference instead.
The 10 MHz reference signal is used to phase lock a 100 MHz VCO. The output
of this VCO is then divided by ten to produce the 10 MHz EXT REF OUT rear
panel signal and also a 10 MHz reference signal for the A16 signal processing
ADC module (SPAM) board. The VCO output is also divided by two to produce
50 MHz reference signals for the A4, A15, and A17 13.5 GHz synthesizer
boards.
Rear-Panel Interconnects
10 MHz REF INPUT (s/n prefixes
<6021 only)
10 MHz REF OUTPUT (s/n prefixes
<6021 only)

A23 Test Set Motherboard

The A23 test set motherboard serves these functions:
— to act as an interface between the A21 CPU board and the auxiliary rear
— to provide ALC signals to the A25 HMA26.5.
Keysight N5224B/25B Service Guide
A BNC connector that allows an external frequency reference signal to be used to
phase lock the analyzer for increased frequency accuracy.
The analyzer automatically enables the external frequency reference feature when
a signal is connected to this input. When the signal is removed, the analyzer
automatically switches back to its internal frequency reference.
A BNC connector that allows a 10 MHz reference signal, produced by the A14
frequency reference board, to be output for use in phase locking external test
equipment.
A BNC connector that allows an external frequency reference signal to be used to
phase lock the analyzer for increased frequency accuracy.
The analyzer automatically enables the external frequency reference feature when
a signal is connected to this input. When the signal is removed, the analyzer
automatically switches back to its internal frequency reference.
A BNC connector that allows a 10 MHz reference signal, produced by the A14
frequency reference board, to be output for use in phase locking external test
equipment.
panel interconnects.
6021 Only)
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