Keysight V3500A, User Manual

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92 V3500A User’s Guide
4 RF Measurement Basics
If the magnitude and phase of the source and load reflection
coefficient are known, this mismatch error can be calculated
and compensated for — completely eliminating mismatch
uncertainty and an error term.
Alternatively, if just the magnitude of the power meter
reflection coefficient is known, we can then exactly calculate
the term in the numerator of the previous equation and
remove its effect on measurement uncertainty. In that case,
the equation becomes:
The error term |1–
Γ
g
Γ
meter
|
2
depends on both the
magnitude and phase of the source and load reflection
coefficients. Frequently, the magnitude of the reflection
coefficient is known or specified, but the phase is unknown.
The error term will reach its maximum value when both
reflection coefficients are real and 180° out of phase. This
maximum error ratio is described by the equation:
The error term will reach its minimum when both reflection
coefficients are real and in- phase. This minimum error ratio
is described by the equation:
With this information — and knowing or estimating the
reflection coefficient of the device under test — estimation of
the mismatch measurement uncertainty is possible.
P
load Z
0
,
1
Γ
g
Γ
meter
–
2
P
load meter
,
1
Γ
meter
2
–
------------------------------ ×
=
MaximumErrorRatio 1
Γ
g
Γ
meter
+
( )
2
=
MinimumErrorRatio 1 Γ
g
Γ
meter
– ( )
2
=