Re: [SI-LIST] : Dual Stripline impedance

Vinu Arumugham (vinu@cisco.com)
Wed, 15 Apr 1998 10:22:23 -0700

For 1.4 mil Cu, 5 mil lines and a dielectric constant of 4.5, the
Synopsys (Viewlogic ADG ) field solver gives

Zdiff ~ 97 ohm for:

Plane
-----------------------
14 mil

--------
| L1 |
--------
10 mil
--------
| L2 |
--------

14 mil
-----------------------
Plane

and,

Zdiff ~ 104 ohm for:

--------
| L1 |
--------
10 mil
--------
| L2 |
--------

Vinu

Magnus Homann wrote:

> Hi all,
>
> We're thinking about using a dual stripline for a differential
> pair. The diff. impedance should be 100ohm.
>
> Have anyone used this before? Or seen it in suggested? Come to think
> of it, it does sound like a good idea (not mine). Now, the hard part
> is getting the right geometry... Any help from various programs or
> books? Any references would very helpful, the only one I found is in
> "Transmission Line Design Handbook", and it is not very clear. Can you
> analyze this with a field solver?
>
> The concept goes like this (cut-through view of the board):
>
> Plane
> -----------------------
>
>
> --------
> | L1 |
> --------
>
> --------
> | L2 |
> --------
>
>
> -----------------------
> Plane
>
> The Zdiff should be between L1 and L2.
>
> Homann