Service Guide E8361-90001 5-9
PNA Series Microwave Network Analyzers Theory of Operation
E8361A Source Group Operation
In band 2, the output of the swept VCO is passed through a divide-by-2 circuit to produce
the output frequencies listed in Table 5-2. In all other bands, the swept VCO signal is sent
directly to the synthesizer output.
At the output, an ALC circuit maintains the power level at −5 dBm ± 2 dB for bands 0–2 or
−1.5 dBm ± 1.5dB for bands 3–26. In all bands, the output is sent to the A17–A20 LO
distribution path and on to the A27–A30 first converters, as the 1st LO signal.
A17 L.O. Multiplier/Amplifier 12 (LOMA 12)
In bands 0–3, the input signal from the A8 fractional-N synthesizer board is passed
through the A17 LOMA 12 unchanged. For all other bands, the signals are doubled,
filtered, and amplified. In bands 8–26, the signals are again doubled, filtered, and
amplified. Together, all of these signal paths create the full output frequency range of
11 MHz to 12 GHz.
A18 Multiplier/Amplifier 24 (MA 24)
In bands 0–10 and 16–19, the 11 MHz to 12 GHz input frequencies are filtered, amplified,
and passed through the A18 MA 24. In bands 11–15, and 20–26, the signals are doubled,
filtered, and amplified.
Together, these signal paths create the full output frequency range of 11 MHz to 24 GHz
that is sent to the A19 splitter.
A19 Splitter
The A19 splitter receives the 11 MHz to 24 GHz LO signal from the A8, A17, and A18 LO
generation chain and divides it into two signals which are routed to the A20 L.O.
distribution assembly (LODA). This splitter configuration provides the highest level of
balance and control of the LO signal.
A20 L.O. Distribution Assembly (LODA)
In the A20 LODA, the LO signal is amplified and split to provide balanced LO signals to
each of the A27–A30 receiver first converters.
A10 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. This VCO is then used
to phase lock a second VCO at 99.5 MHz. It is also used to provide the 10 MHz EXT REF
OUT rear panel signal, a 20 MHz reference for the A11 phase lock board, and a 5 MHz
reference for the A6 signal processing ADC module (SPAM) board, the A8 fractional-N
synthesizer board, and the A9 fractional-N synthesizer board (Option 080 only).
The 95.5 MHz reference signal is sent through a divide-by-3 circuit to produce the fourth
multiple of the 8.21966 MHz 2nd LO signal (33.1667 MHz) for bands 1-26 which is sent to
the A35 receiver motherboard.
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