Teledyne LeCroy VirtualProbe User Manual
Page 11
Operator's Manual
Transmission Line - Select to use a lossless transmission line modeled by its delay and characteristic
impedance.
Touchstone File - Select to use S-parameters to represent the block. The Touchstone file should follow
the Touchstone 1 format, and should also meet requirements described in
.
When you select Touchstone File, the additional settings described below are enabled.
Touchstone File Block Type
If you choose to define a block by importing a Touchstone file of S-parameters, these additional controls
will appear:
NumFiles - This selector is visible when the setup/lane is configure for 4 ports. See
for port
setup information. Choose "1" to use a 4-port touchstone file, or "2" to use two 2-port touchstone files.
Using two 2-port files is typically done when looking to describe the block using two transmission lines
(such as cables) between which there is no meaningful crosstalk, such that using two 2-port S-parameters
files is an accurate model for the block.
Format - This selector is visible when the setup/lane is configure for 4 ports. (See
for port
setup information). In the unusually circumstance in which the S-parameters where saved in a mixed-
mode format, select "Mixed mode".
NOTE: The Touchstone 1 format is not designed for mixed-mode S-parameters, and using Touchstone
1.0 to store mixed-mode S-parameters is NOT recommended. While it is certainly important to under-
stand mixed-mode characteristics of differential interconnects, Teledyne LeCroy highly recommends sav-
ing your S-parameters in single-ended format in order to prevent any future confusion.
Touchstone File Port Mapping - The diagram in this section of the dialog will adapt to the settings for
NumPorts, NumFiles, and Format. Configure the port number selectors in the diagram to correctly map
the port numbers in the S-parameters file(s) to the input and output ports of the block.
NOTE: if the VirtualProbe output is extremely distorted, then it is possible that the ports were not
assigned correctly.
Mapping for four-port network specified in one file.
Mapping for four-port network specified in two files.
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