5-12 Keysight N5224A/25A Service Guide
Theory of Operation
Synthesized Source Group Operation
5-
For bands 16–18, the input signals of all four doubler boards are amplified and
filtered, then sent to the doubler board output.
For bands 19–30, the input signals of all four doubler boards are doubled,
amplified and filtered, then sent to the doubler board output.
Doubler board output signals for bands 2–30 create the full synthesized source
output frequency range of 10 MHz to 50 GHz.
The A7 50 GHz doubler board provides an EXT TSET DRIVE RF1 OUT signal to
the rear panel. This signal is output at a frequency range of 3.2–19 GHz for use
with an external test set. This output is terminated with a 50-ohm load on the
A8, A12, and A13 doubler boards.
The companion signal, EXT TEST SET DRIVE LO, is output from the A27 mixer
“A27 and A28 Mixer Bricks” on page 5-22
.
A25 Multiplier/Amplifier 26.5 Board (HMA26.5)
for band numbers and frequencies discussed
here.
In bands 2–15 and 23-25, the synthesized LO input is filtered, amplified, and
passed through to the A26 splitter (4-port only). In bands 16–22 and 26-30,
the input is amplified, doubled, and filtered, then sent to the output.
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.
A14 Frequency Reference Board
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.
