I have created a differential channel with microstrip transmission line with CILD. I have also extracted the s-parameter file (.s4p) file for the corresponding transmission line. I actually will need this .s4p file to use in cadence. I was checking the TDR impedance of the transmission line and the of the extracted s-parameter file of my transmission line. Somehow it doesn't match in the beginning.
My s-aparameter touchstone file format generated in ADS using conventional method of 4 port of 50 ohm each.
My test bench to compare the TDR impedance varies for my Transmission line and corresponding s-parameter file:
S-parameter port mapping:
The resulting TDR impedance plot of both:
You can see, till 4ns, the impedance is not same, but I used the same equation to get the impedance. Can anyone help me to know why did this happened and what to do to fix it?