Specifications
Measurement calibration using the MS462XX is
straightforward and menu directed. A short time
spent in preparation and preplanning will make the
process simple and routine. (Example: Adjusting the
coaxial cables used in the measurement setup such
that insertion of the DUT causes minimal flexing of
these cables).
The screen prompts on the MS462XX guide you
through the calibration process—a process that con
-
sists of connecting and disconnecting connectors and
moving the slide on a sliding load (if one is used).
The most critical part of the calibration process is
properly seating and torquing the connectors. Also,
you will notice that the calibration takes longer
when the ports are terminated with a load. This is
intentional. It allows for more averaging during the
isolation measurement.
Calibrating for
a Measurement
Let us assume that we want to correct for three er-
rors in the reflection measurement: source match,
directivity, and tracking. We accomplish this using
three standards.
Shorts are the easiest to visualize. They totally re-
flect all of the incident RF energy output at a pre-
cise phase. The terms zero-ohms impedance, voltage
null, and 180° phase all define an RF Short.
Opens are similar to Shorts, but their response is
more complex. The terms voltage maximum, infinite
impedance, and 0° phase all define a perfect Open. A
perfect Open, however, is only a concept. In reality
Opens always have a small fringing capacitance.
To account for the fact that the Open will not pre
-
dictably reflect impedance at an exact 0° phase ref
-
erence, we alter its response using coefficients that
accurately characterize the fringing capacitance.
The coefficients are different for each coaxial line
size, since each size has a different fringing capaci
-
tance. To maximize accuracy, ensure that these coef
-
ficients are installed prior to the calibration
(Menu U3).
As Opens and Shorts provide two references for a
full reflection, Z
0
terminations provide a
zero-reflection reference.
MEASUREMENT MEASUREMENT CALIBRATION
CALIBRATION DISCUSSION
MS462XX OM 7-9
CALIBRATING FOR A REFLECTION
MEASUREMENT USES THREE
STANDARDS:
l Short
l Open
l Termination