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PNA Series Microwave Network Analyzers
Theory of Operation
N5230A
Synthesized Source Group Operation
Frequency Offset Operation (Option 080)
Since the A7 and A9 fractional-N synthesizer boards each contain their own phase lock
circuitry, they can be phase locked independently to different output frequencies. Normally
the LO signal is automatically tuned to a frequency 7.66 MHz higher than that of the test
signal to create the 7.66 MHz difference frequency (IF) in the A20 mixer brick.
In frequency offset mode (Option 080), the LO signal can be independently tuned to any
frequency (within its tuning range) to allow for frequency offset measurements needed
when testing devices such as mixers and converters.
A7 and A9 Fractional-N Synthesizer Boards
The A7 and A9 fractional-N synthesizer boards use the 5 MHz reference signal from the
A10 frequency reference board to tune two VCO circuits: one that sweeps from 1500 to
3125 MHz and one that is set to a CW frequency of 2250 MHz.
In bands 0–3, these signals are mixed to produce the output frequencies listed in
Table
5-2.
In band 4, 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. In all bands, the output is sent to either the A6 or A8
multiplier board.
The output of the A7 fractional-N synthesizer board is 7.66 MHz higher than the output of
the A9 fractional-N synthesizer board. This is because the output of the A7 fractional-N
synthesizer board is routed through the A6 multiplier board to the A20 mixer brick where
it is mixed with the test signal to produce a 7.66 MHz IF signal for each of four channels.
Refer to
"A20 Mixer Brick" on page 5-19
for a more complete description.
A6 and A8 Multiplier Boards
In bands 0–5, the input signal from the A7 or A9 fractional-N synthesizer board is passed
through the multiplier board unchanged. For all other bands, the signals are doubled,
filtered, and amplified. In the A6 board, in bands 9 and 10, the signals are again doubled,
filtered, and amplified. In the A8 board, in bands 9, 10, and 12, the signals are again
doubled, filtered, and amplified. Together these signals create the full output frequency
range of 300 kHz to 10.508 GHz for the A6 board or 300 kHz to 10.5 GHz for the A8 board.
A19 Switch/Splitter/Leveler/Amplifier/Multiplier (SSLAM)
In bands 0–10, the 300 kHz to 10.5 GHz inputs are filtered, amplified, and passed through
the A19 SSLAM. In bands 11 and 12, they are doubled, filtered, and amplified.
Together, these signal paths create the full output frequency range of 300 kHz to 6 GHz or
300 kHz to 13.5 GHz that is sent to the splitter where a portion of the signal is used for the
R1 and R2 reference channel signals and another portion for the ALC circuit on the A16
test set motherboard.
Service Guide N5230-90014
5-9
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Troubleshooting
