Agilent Technologies 8753ET User Manual page 413

TRL Options
The
TRL/LRM OPTION
selections under this menu:
• (calibration Z
CAL ZO:
• (set reference)
SET REF:
The characteristic impedance used during the calibration can be referenced to either the
line (or match) standard (
The analyzer defaults to a calibration impedance that is equal to the line (or match)
standard.
When the
CAL ZO: LINE ZO
assumed to match the system impedance exactly (the line standard is reflectionless). After
a calibration, all measurements are referenced to the impedance of the line standard. For
example, when the line standard is remeasured, the response will appear at the center of
the Smith chart. When
(under menu) and
Cal
CAL ZO: SYSTEM ZO
the impedance of the line standard. This requires a knowledge of the exact value of the Z
of the line. The system reference impedance is set using
menu. The actual impedance of the line is set by entering the real part of the line
impedance as the
OFFSET ZO
was known to have a characteristic impedance of 51 Ω (
be used to calibrate for a 50 Ω measurement (
measurements would be referenced to 50 Ω, instead of 51 Ω. When the line standard is
remeasured, the center of the Smith chart is at the current value of
50 Ω). Since only one value of offset Z
should be a constant value over the frequency range of interest in order to be meaningful.
The location of the reference plane is determined by the selection of
SET REF: REFLECT
must have a known insertion phase or electrical length. If a non-zero length thru is
specified to have zero delay, the reference plane will be established in the middle of the
thru. The reflect standard may be used to set the reference plane instead of the thru
provided the phase response (offset delay, reactance values and standard type) of the
reflect standard is known and is specified in the calibration kit definition.
softkey accesses the TRL/LRM options menu. There are two
)
0
CAL ZO: LINE ZO
is selected, the impedance of the line (or match) standard is
CAL ZO: LINE ZO
(within the define standard menu) are ignored.
OFFSET ZO
is selected when the desired measurement impedance differs from
within the define standard menu. For example, if the line
can be selected for the line standard, the value of Z
0
. By default, the reference plane is set with the thru standard which
TRL*/LRM* Calibration (ES Models Only)
) or to the system (
CAL ZO: SYSTEM ZO
is selected, the values entered for
SET ZO
OFFSET ZO
= 50 Ω). After a calibration, all
SET ZO
Operating Concepts
SET ZO
under the calibration
= 51 Ω), it could still
(in this case,
SET ZO
and
SET REF: THRU
7-75
).
0
0