11.6 Port extension
The Port extension feature allows you to mathematically move the reference plane of a reflection or
impedance measurements. This can be useful if Open/Short/Load calibration cannot be performed
directly at the point of connection of the DUT. There could be a short transmission line on a PCB but
the Open/Short/Load calibration has been performed at the point of the cable-connector.
Port extension allows you to enter a physical length L and the propagation speed respectively the
velocity factor VF. The velocity factor VF is the ratio between the speed of light c and the propagation
speed of the signal on the transmission line / cable. It is a number between zero and one. The time
needed for the signal to travel along that transmission line can then be calculated by:
Assuming zero loss, the reflection factor at the end of that transmission line can be calculated as:
Using port extension
To use Port extension the first time, you must enable it in the Options dialog. You can find the option in
the options menu under the Advanced section.
After having Port extension enabled, you will find the Port extension icon in the Home ribbon besides
the calibration icons.
You can enable or disable Port extension by clicking on the icon. A green icon indicates that the Port
extension calculation is active.
Port extension is not active (no
colored background).
Port extension is active (green
colored icon background).
By clicking on the lower part of the icon you can open the port extension configuration
window. To do so, click on configure port extension as shown below.
Bode Analyzer Suite software features
OMICRON Lab
141
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