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Theory of Operation
Synthesized Source Group Operation
Synthesized Source Group Operation
The source group produces a stable output signal by phase locking a synthesized voltage-controlled
oscillator (VCO). Refer to
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
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
•
A19 Test Set Motherboard
Basic Operation
Table 5-1 on page 5-8
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
"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
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 than the test signal. Since the A4, A13, and A11
13.5 GHz synthesizer boards each receive their 50 MHz input reference signal from the exact same source,
frequency drift error is eliminated.
5-6
Table 5-1 on page 5-8
for the full frequency range of the source. The outputs at the
5-7.
(including rear-panel interconnects)
(including rear-panel interconnects)
PNA Series Microwave Network Analyzers
Chapter 4,
Service Guide N5222-90001
N5221A/22A
D and
–
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Table of Contents
Troubleshooting
