Keysight Technologies N5221A, Руководство по обслуживанию

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5-6 Keysight N5221A/22A Service Guide
Theory of Operation
Synthesized Source Group Operation
5-
Synthesized Source Group Operation
The source group produces a stable output signal by phase locking a
synthesized voltage-controlled oscillator (VCO). Refer to Table 5-3 on
page 5-9 for the full frequency range of the source. The outputs at the front
panel test ports are swept, stepped or CW signals. For a simple block diagram
of the source group, refer to Figure 5-3 on page 5-8 .
In this section the following are described:
— Basic Operation
— A4, A13, and A11 13.5 GHz Synthesizer Boards
— A5 and A8 26.5 GHz Source Boards
— A21 Multiplier/Amplifier 26.5 Board (HMA26.5)
— A10 Frequency Reference Board (including rear-panel interconnects)
— A19 Test Set Motherboard (including rear-panel interconnects)
Basic Operation
Table 5-3 on page 5-9 lists the L.O. harmonic number, the synthesizer
frequencies (A4, A13, and A11), and the main source frequency (A5 and A8)
within the analyzer for each band. This table is referred to throughout this
chapter and also appears on the overall block diagram at the end of Chapter 4,
“Troubleshooting.”
The A10 frequency reference board produces a constant phase locked
reference signal of 50 MHz that is sent to the A4, A13, and A11 13.5 GHz
synthesizer boards.
The A11 13.5 GHz synthesizer board produces an LO signal that is sent through
the A21 multiplier/amplifier 26.5 to the A23 and A24 mixer bricks (via the A22
splitter). The frequency is synthesized such that the mixing product of this LO
signal with the test signal output is a constant 7.438 MHz IF; except for
frequencies below 53 MHz when the IF is 0.826 MHz. This IF signal is sent to
the A12 SPAM board for digital processing.
The A4 and A13 13.5 GHz synthesizer boards each produce an incident signal
that is sent to the front panel outputs. A portion of these signals are coupled off
and sent to the A23 and A24 mixer bricks (A–D and R1–R4) where they are
mixed with the LO signal from the A22 splitter to produce the 7.438 MHz (or
0.826 MHz) IF signal.
The A4, A13, and A11 13.5 GHz synthesizer boards each contain their own
phase lock circuitry. The A11 board is used to phase lock the LO signal while
the A4 and A13 boards are used to phase lock the test signal. This makes it
possible for the LO signal to be tuned to a different frequency than the test
signal, which is necessary since the LO signal is normally 7.438 MHz higher