Configuration 3 - Agilent Technologies AN 1287-6 Application Note

Configuration 3

Configuration summary
• Medium complexity
• Boosted source
• Forward transmission measurement only
• Response calibration only
Setup and features
Compared to Configuration 2, Configuration 3
improves measurement uncertainty and flexibility
by measuring the incident signal after the booster
amplifier rather than before. Measuring the inci-
dent signal after the booster amplifier ratios out
the effects of any source mismatch.
Boost the analyzer's source power by connecting
the booster amplifier to the "RF out" port on the
analyzer. An external coupler connected to the
output of the booster amplifier directs a portion of
the boosted source signal to the R channel of the
analyzer. This signal becomes the reference signal
used in ratioing (Configuration 3).
Network analyzer
1
Booster
amplifier
Coupler
DUT
DUT
Calibration points
Configuration 3
2 R in
Attenuator
Attenuator
Measuring the reference signal after the amplifier
ratios out any mismatch ripple between the booster
amplifier and the DUT and any drift or power
fluctuations of the booster amplifier. The reverse
isolation of the booster amplifier makes forward
reflection measurements and reverse transmission
measurements impossible.
In configurations where the user provides an
R channel signal, determining the proper level is
important. Too low a signal level can be affected by
noise and can cause phase-locking problems and
inaccurate measurement results. Too high a signal
level can be affected by receiver compression,
causing inaccurate results. The receiver can also
be damaged if the signal is high enough. To find
the proper signal level for the R channel (a typical
range might be 0 to –30 dBm) look at the analyzer's
specifications. Then determine the signal level at
the coupled arm of the coupler, and add attenua-
tion to achieve the proper signal level at the
R channel.
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