Agilent Technologies 8719D, User Manual

Page: 367 / 673

For the reflect step, identical high reflection coefficient standards (typically open or short
circuits) are connected to each test port and measured and
For
the
line step, a short length of transmission line (different in length from the thru) is
inserted between port 1 and port 2 and again the frequency response and port match are
measured in both directions by measuring all four S-parameters.
In total, ten measurements are made, resulting in ten independent equations. However, the
error model has only eight error terms to solve for. The characteristic impedance of the
line standard becomes the measurement reference and, therefore, has to be assumed ideal (or
known and defined precisely).
At this point, the forward and reverse directivity
and transmission tracking (Err
and and reflection tracking and terms may be derived from the error
terms. This leaves the isolation and source match and and load match
and terms to discuss.
Two additional measurements are required to solve for the isolation terms and
Isolation is characterized in the same manner as the Full calibration. Forward and
reverse isolation are measured as the leakage (or crosstalk) from port 1 to port 2 with each port
terminated. The isolation part of the calibration is generally only necessary when measuring
high loss devices (greater than 70
Note
an isolation calibration is performed, the leakage must be the
same during the isolation calibration and the measurement.
.
=
=
= =
Figure 6-54. S-term error model and generalized
Application and