Learning Forum

[alexandre-antoi.bourrieau]

Hello,

I am trying to simulate a 100 ohm differential impedance FCC flat cable (Molex) but I can't find consistent results when using the Lumped or Wave terminal ports.

 

My aim is to simulate 24 inches long cable. But as it is very processor demanding, I want to simulate a portion of the cable (here 5 cm) and virtualy increase the lenght of the cable by de-embeding it.

 

Problem is I cannot use lumped ports because using lumped port do not give the possibility to use de-embeding for extend lenght of cable. So I need to to use wave ports.

The structure of the cable  is following and I am trying to simulate common signal to get 50 ohm impedance :

When using terminal Lumped port, I got 50 ohm result for a single signal with two GND around it (GND/ SIG / GND ) which is consistent with the 100 ohm diff cable :

Unfortunatly, when using terminal wave port, I got 38 ohms instead of 50 :

I have tried to modify a little the port geometry so that there is 3 digit scale for the E-field on the wave port, and a better e-filed vector distribution but I still get 38 ohm instead of 50 ohm...

Do someone have any idea to get better result using wave port ?

 

Thanks you very much !

[alexandre-antoi.bourrieau]

I think the geometry for my port is OK because if I increase it like this, I got oscillation on the TDR response, but still 38 ohms: