Inconsistent results between Terminal Wave Port and Terminal Lumped Port when simulating a flat FCC cable ... can someone help me ?

[rdpdo2002]

Hello,

I would like to simulate the system {connector1 + 24 inches cable + connector2}, something like this :

Obviously, I cannot simulate this because of the computing cost....


But under HFSS, I can use deembedinbg using wave ports (but not using lumped ports) so my idea is to simulate :
- the S-parameters of the connector1 inputs / output
- a little length of cable using wave ports
- dembed to get the 24 inches lenght of cable
- the S-parameters of the connector2 inputs / output (which are the same as connector1)
- Add all the circuits in series

I am just wondering if I can add the S-parameters circuits in series and if it is correct to add them to get the total system s-parameters ?

Thanks you for your advice

 

[D.A.(Tony)Stewart]

You can simulate anything if you have tested it for the Zo and crosstalk or have all the L/C parameters.

Is it 200 ohm or shielded 100 ohm cable or ?

 

[rdpdo2002]

Hello,

It's a shield 100ohms differential cable
I can get the Z by TDR.

Thanks

 

[rdpdo2002]

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...

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:

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

Thanks you very much !