Keysight U2020 X Series - Gamma Correction; Figure 2-28 Device-Under-Test (DUT) to U2020 X-Series Connection Diagram

General Operating Information 2
Keysight U2020 X-Series User’s Guide 65
Gamma correction
Figure 2-28 Device-Under-Test (DUT) to U2020 X-Series connection
diagram
In a realistic measurement environment, the DUT impedance or the reference
impedance (Z
o
) is not equal to the U2020 X-Series impedance. The mismatch in
impedance values causes a portion of the signal voltage to be reflected. This is
quantified by the reflection coefficient, or Gamma (Γ). A portion of the incident
power to the U2020 X-Series, P
i
, is reflected back to the DUT as P
r
. The remaining
power, P
d
, gets delivered to the U2020 X-Series. A generic DUT will reflect part of
P
r
back to the U2020 X-Series, and the reflected portion will be superimposed
onto P
i
. The nominal power, P
zo
(the power generated after factoring in Z
o
) may
be calculated as follows:
Gamma correction compensates for impedance mismatch via two options, which
are Single Point Gamma and Table-Based Gamma.
NOTE
The Gamma correction function is only available in U2020 X-Series power
sensors with firmware version A.04.04 and above.
U2020 X-Series
DUT
Γ
DUT
Γ
L
P
r
P
i
P
d
U2020 X-Series
Γ
L
≠ 0
P
zo
P
i
1 Γ
DUT
Γ
L
–
2
=