Agilent Technologies 8719D User Manual page 367

For the reflect step, identical high reflection coefficient standards (typically open or short
circuits) are connected to each test port and measured (Sll and $2).
For line step, a short length of transmission line (different in length from the thru) is
the
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
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 (Eur and Eun), transmission tracking (Err
and Em), and reflection tracking (Em and Em) terms may be derived from the TRL' error
terms. This leaves the isolation (EXF and ExR), source match (Esr and Esn) and load match
Two additional measurements are required to solve for the isolation terms (EXF and ExR).
Isolation is characterized in the same manner as the Full 2-port 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 dB).
Note
same during the isolation calibration and the measurement.
Figure 6-54. S-term TIC* error model and generalized coefficients.
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