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Configuration 1
Configuration summary
• Low complexity
• No boosted source
• Forward and reverse measurements
• Full two-port or response calibration
Setup and features
The simplest high-power devices to measure are
those that have high gain but don't require high
levels of drive power, and typically are tested in
their linear region. Since these devices have high
gain, the receiver must be protected from the high
output power. An attenuator or coupler added
between the output of the DUT and the analyzer's
test port protects the receiver. If using a coupler,
terminate the through arm of the coupler with a
characteristic impedance load. The coupled arm of
the coupler sends a small portion of the input sig-
nal to port 2. For a 20-dB coupler, the signal at the
coupling arm is 20 dB less than the strength of the
signal at the input. Determine the maximum power
out of the DUT, subtract the power level required
at the test port, and then choose the appropriate
attenuator or coupler value. Choose components
that are specified to handle your chosen power level.
Configuration 1 makes both forward and reverse,
reflection and transmission measurements (S
S
, S
, and S
) if using an analyzer with an
12
21
22
S-parameter test set.
Calibration
This particular setup allows both forward and
reverse measurements so full two-port error-
correction, the most accurate calibration, can be
performed. Calibration is performed at test-port 1
(or at the end of the cable attached to the port)
and at test-port 2 (with the attenuator and any test
cable). Include the attenuator or coupler on port 2
when performing the calibration to remove any
mismatch between the attenuator and the analyzer's
test port. Since calibration is performed with all
hardware in place and all error terms corrected,
the measurements can be as accurate as the
standard analyzer.
6
Configuration 1
The attenuator on port 2 degrades the uncorrected
directivity of port 2 by twice the attenuation value.
This limits the stability of the calibration and
can make S
measurement is needed, calibrate at a higher
power level, lower the power level when making
forward measurements, and then raise the power
level for the reverse measurements. There is more
information on calibrating and power levels at
the end of this note.
A common assumption is that the DUT's displayed
gain should be increased by the amount of the
attenuation, but remember that the calibration
,
includes the attenuator so the values as displayed
11
are correct.
Network analyzer
1
2
DUT
Calibration points
measurements very noisy. If an S
22
Attenuator
22
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