Keysight Technologies N5221A, Service Manual, Page: 134 / 368

5-10 Keysight N5221A/22A Service Guide
Theory of Operation
Synthesized Source Group Operation
5-
Refer to Table 5-3 and Figure 5-3 for band numbers and frequencies discussed
here.
In bands 2-10, the output of the swept VCO is passed directly or through a
divide-by-2, 4, or 8 circuit to produce the output frequencies as listed in Table
5-3 .
In band 6, the output of the swept VCO is passed through a divide-by-4 circuit
and then sent to a Direct Digital Synthesizer to produce the output frequencies
for bands 2-4 as listed in Table 5-3 .
In bands 11-21, the swept VCO signal is passed through a doubler circuit
where the signal for some bands are sent directly to the output of the
synthesizer board while other bands are passed through another doubler
circuit then to the output of the synthesizer board to produce the output
frequencies listed in Table 5-3 .
The output of the A11 13.5 GHz synthesizer board (the LO synthesizer) is 7.438
MHz higher than the output of the A4 and A13 13.5 GHz synthesizer boards
(the source synthesizers). This is because the output of the A11 13.5 GHz
synthesizer board is routed through the A21 LO multiplier/amplifier 26.5 board
to the A23 and A24 mixer bricks where they are mixed with the test signals to
produce a 7.438 MHz IF signal for each of eight receivers (A–D and R1–R4).
Refer to “A23 and A24 Mixer Bricks” on page 5-21 for a more complete
description.
A5 and A8 26.5 GHz Source Boards
In bands 2–9, the input signals from the A4 or A13 13.5 GHz synthesizer board
are passed through to both outputs (main and secondary) unchanged.
For bands 10-15, the input signals are passed directly to the secondary output
or amplified and filtered, then sent to the main output.
For bands 16-21, the input signals are doubled, filtered, and amplified. The
signals for these bands are then either passed directly to the secondary output
or passed through more amplification and filtering and sent to the main output.
Together these signals for bands 2–21 create the full synthesized source
output frequency range of 10 MHz to 26.5 GHz. These output frequencies for
each band are listed in Table 5-3 .
The A5 26.5 GHz source board provides an EXT TSET DRIVE RF OUT signal to
the rear panel. This signal is output at a frequency range of 3.2–26.5 GHz for
use with an external test set. This output is terminated with a 50-ohm load on
the A8 26.5 GHz source.
The companion signal, EXT TEST SET DRIVE LO, is output from the A23 mixer
brick. Refer to “A23 and A24 Mixer Bricks” on page 5-21 .