Keysight N5224B, Руководство по обслуживанию

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5-20 Keysight N5224B/25B Service Guide
Theory of Operation
Synthesized Source Group Operation
5-
A4, A15, and A17 13.5 GHz Synthesizer Boards (S/N Prefixes
<
6021
Only)
The A17 13.5 GHz synthesizer board is included only on 4-port models.
The A4, A15, and A17 13.5 GHz synthesizer boards use the 50 MHz reference
signal from the A14 frequency reference board to tune a VCO circuit that
sweeps from 2 GHz to 4 GHz.
Refer to
Table 5-6 and Figure 5-6 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
5-6 .
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 5-6 .
In bands 11-30, 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 5-6 .
The output of the A15 13.5 GHz synthesizer board (the LO synthesizer) is 7.438
MHz higher than the output of the A4 and A17 13.5 GHz synthesizer boards
(the source synthesizers). This is because the output of the A15 13.5 GHz
synthesizer board is routed through the A25 LO multiplier/amplifier 26.5 board
to the A27 and A28 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 “A27 and A28 Mixer Bricks” on page 5-47 for a more complete
description.
A15 Version 7 Digital to Digital Synthesizer (DDS) Assembly (S/N
Prefixes
≥
6021 Only)
For instruments with s/n prefixes
≥
6021, there are three A15 Digital
Synthesizer (DDS) assemblies: N5240-60222 contains two DDS chips
(standard 2-port, N5240-60223 assembly contains four DDS chips (standard
4-port), and an optional N5240-60102 containing a four DDS chip assembly, is
required for adding a 3rd source (Option XSB).
The A15 Direct Digital Synthesizer (DDS) assembly uses an internally
generated 10 MHz reference signal that is derived from the 100 MHz OCXO
circuit (if present, this signal may be locked to an external reference).
The 100 MHz OCXO signal is coupled off to a divide-by-10 section and the
resulting 10 MHz synchronized clock-signal is output from the DDS carrier
board to the input of the A16 SPAM board (SPAM CLK) and to the rear panel
(REF OUT).