Concepts and Features
R&S
®
ZNB/ZNBT
137
User Manual 1173.9163.02 ─ 38
(TOSM, ...) calibration is available for the specified port, it is possible to export
the data even when the trace is not displayed.
–
For a multiport Touchstone file
*.s<n>p
, either a full multiport system error
correction or a complete set of n
2
S-parameters must be available. If the port
configuration contains balanced ports, the exported Touchstone file contains
the converted single-ended S-parameters.
This type of export can be initiated from the GUI by using the "s<n>p Port ..." or
"snp Free Config. ..." functions of the TRACE > TRACE CONFIG > "Trace Data"
softtool or by the remote command
MMEMory:STORe:TRACe:PORTs
.
Renormalization of S-parameters
Renormalization means that the S-parameters at connector impedances are converted
into S-parameters at certain target impedances. During export the S-parameters can
be renormalized in two ways: either a common target impedance is used for all ports or
the individual port reference impedances are used.
If the reference impedances are identical and real this common resistance value is
used as reference resistance of the Touchstone option line. Otherwise the value 50 Ω
is used.
●
Common Target Impedance
For multi-port S-parameters the reference resistance of the Touchstone option line
is taken as common target impedance and the data is renormalized to the common
target impedance, regardless of the port reference impedances. Thus in case of
ambiguous port reference impedances the data is always renormalized to 50 Ω.
●
Port Reference Impedance
The
Chapter 4.3.6, "Reference Impedances"
on page 125 of the individual ports
are used as target impedances for the renormalization. The target impedances are
listed in a comment line in the Touchstone file; if the related ports use different ref-
erence impedances, an additional comment with a warning is added that the
Touchstone option line contains a non-matching reference resistance (see exam-
ple below).
Note
that when re-importing this type of file into standard applications (including
the R&S
ZNB/ZNBT itself), the reference resistance from the Touchstone option
line is used and the impedance system underlying the data will not be interpreted
correctly.
Example: Renormalization comments
!The following Port Impedance Renormalization has been used when saving the data.
!PortZ Port1:50+j0 Port2:70+j0
!Note: The Port Impedances differ from the reference impedance of this file.
! While reading the file the reference impedance value of the option line above
! is always used.
Touchstone files cannot be used to export mathematical traces.
Operations on Traces