Keysight N5221A Service Manual page 315

PNA Series Microwave Network Analyzers
N5221A/22A
Figure 8-4 Flowgraph of Four-Port Error Terms
where:
E = error term
DIR = Directivity
MAT = Forward Source Match and Reverse Load Match
TRK = Forward Reflection Tracking and Reverse Transmission Tracking
For the case of a full 4-port calibration, port 1 has
four Match error terms:
S11 source match
S12 load match
S13 load match
S14 load match
and four Tracking error terms:
S11 reflection tracking
S12 transmission tracking
S13 transmission tracking
S12 transmission tracking
There are eight isolation (crosstalk) terms not shown.
Service Guide N5222-90001
General Purpose Maintenance Procedures
Error Terms
8-7