## PCB differential vias

**Moderator:** thorsten

### PCB differential vias

Has anyone attempted modeling differential vias on a PCB to obtain 4 port S-parameters?

### Re: PCB differential vias

Can you be a bit more specific? 4 port S-Parameter are no problem, but what do you mean by

regards

Thorsten

?differential vias on a PCB

regards

Thorsten

### Re: PCB differential vias

Thanks for the reply,

Differential vias are a pair of vias on a printed circuit board that share a common anti-pad. They are used to transition a differential pair between layers.

http://www.ee.washington.edu/research/l ... 091707.pdf

Actually, If there is an example of a single PCB via that is available that would be very helpful too.

Thanks

Differential vias are a pair of vias on a printed circuit board that share a common anti-pad. They are used to transition a differential pair between layers.

http://www.ee.washington.edu/research/l ... 091707.pdf

Actually, If there is an example of a single PCB via that is available that would be very helpful too.

Thanks

### Re: PCB differential vias

Hi,

doesn't look to complicated to do?

The vias would just be cylinders and the antipad (it means missing metal right?) could be modeled using a polygon (of air with a higher priority than the metal) ...

What does this have to do with 4-port S-Paramters?

regards

Thorsten

doesn't look to complicated to do?

The vias would just be cylinders and the antipad (it means missing metal right?) could be modeled using a polygon (of air with a higher priority than the metal) ...

What does this have to do with 4-port S-Paramters?

regards

Thorsten

### Re: PCB differential vias

4 port s-parameters is the conventional way this structure is conveyed to signal integrity simulators. Same way that a single via would be a 2-port s-parameter (one port at each end of via, each ground referenced).

Normally HFSS and ADS are used for this (neither of which I have). I was just wondering if anyone has gotten satisfactory results modeling this with openEMS.

Thanks

Normally HFSS and ADS are used for this (neither of which I have). I was just wondering if anyone has gotten satisfactory results modeling this with openEMS.

Thanks

### Re: PCB differential vias

Instead of ADS, use qucs to do circuit level simulations.

OpenEMS can be used to extract the via behaviour: use AddMSLPort to create the needed number of ports and process them with calc_ypar. This gives you the Y matrix, which can be transformed into S parameters. To get accurate results, the mesh needs to be fine.

A 2.5 D solver is more suited for this kind problem, check Sonnet.

Sebastian

OpenEMS can be used to extract the via behaviour: use AddMSLPort to create the needed number of ports and process them with calc_ypar. This gives you the Y matrix, which can be transformed into S parameters. To get accurate results, the mesh needs to be fine.

A 2.5 D solver is more suited for this kind problem, check Sonnet.

Sebastian