Network analyzer Port extension question

Hi all,

i understand that the port extension mean to extend the reference plane of our measurement so that we can get accurate measurement.
So normally i used "auto port extension" function(as shown in the pic below) to do port extension either measured short or open.
now the the questions are what are those "extension port 1" with electrical delay and also the "loss" tab in the picture shown below.
thanks!

Depends on what software and VNA you are using.
Port selection can selects S11 port as either port 1 or port 2 if you VNA alternatively can use port 2 for S22.
Guess auto port extension is just adding timing delay.
Adding cable length do also add cable loss which maybe can be compensated for by pushing button [Loss]. What happens when you push that button?
Exact function of each button is most likely described in software manual.

Educated guess: If you are using a "certified" calibration tool for VNA which may be pre-defined(some VNA's ask for which calibration you use), then it may subtract the effects of calibration open/short from measurements.

Think of ports as your eyes and in the circuit; and when u calibrate a VNA(it may inclue cables or not), end of the part which u performed calibration becomes your eyes. Then you add some adaptors or jack-to-sma interconnects to the DUT. When you are adding the adaptors, each adaptor presents an "electrical length" and "insertion loss" for their imperfections. Port extension meaning is that u write the "electrical length" and "loss" of those parts into your measurements to account for *phase difference (mostly) in your setup. When thinking about magnitude, port extension does not make sense(most of time); but If you are insterested in "phase" then it's useful.

i know what is port entension, i just dont understand what the function of the "loss" tab in the menu there.

Instead of "Loss", read "External Loss" and this will explain everything.

arr_baobao said:

i know what is port entension, i just dont understand what the function of the "loss" tab in the menu there.

Click to expand...

I guess the "loss" here actually stands for the loss of the extension cable. The instrument use the "length" and "loss" to estimate the s-parameter of the extension cable, then use the estimated s-parameter to subtract the side-effect caused by the extension cable.

cariban said:

I guess the "loss" here actually stands for the loss of the extension cable. The instrument use the "length" and "loss" to estimate the s-parameter of the extension cable, then use the estimated s-parameter to subtract the side-effect caused by the extension cable.

Click to expand...

how it measured loss when it just a 1 port. just curious.

If extension cable is shortened in its outer end is VNA adding correction so that impedance with 0 Ohm is read.
If extension cable is left open is its outer end is VNA adding correction so that impedance with infinite Ohm is read.
Value that is read is an cable reflection and same port is both Tx and Rx.
For S11 do such compensation differ compared S21 as resistive Ohmic loss must be compensated for twice, one for each signal direction.