[SI-LIST] Re: Lower epsilon achieves lower crosstalk
- From: ZHENGGANG CHENG <zhenggang.cheng@xxxxxxxxx>
- To: Liu Xike <xike.silist@xxxxxxxxx>
- Date: Thu, 11 Nov 2010 11:25:52 -0800
Hi Liu,
Xtalk analysis is very different for microstrip and stripline cases, and it
also depends what xtalk you are talking about such as FEXT or NEXT.
For stripline, there is no FEXT, and NEXT proportional to Cm/C. So in this
case, lower Er, to keep the same impedance, H will be decreased, so Cm/C
will be smaller.
For microstrip case, FEXT is proportional to Cm/C-Lm/L, and NEXT is
proportional to Cm/C+Lm/L. In your case, Lm/L is becoming larger (Lm is not
changing, L is decreased due to smaller H), Cm/C may be smaller, then FEXT
will become larger due to lower Er.
Zhenggang CHENG
On Wed, Nov 10, 2010 at 10:46 PM, Liu Xike <xike.silist@xxxxxxxxx> wrote:
> We could achieve lower crosstalk by using dielectric with lower
> permittivity, while keeping *Z0* as a constant.
>
>
> I'm new in SI, my understanding about this question is:
>
>
>
> If we use dielectric with lower permittivity while keeping *Z0* as a
> constant.
>
> We need to reduce *h *to maintain a constant *C*, because *C*> *epsilon***w*
> /*h*, and *Z0*=1/*vp*/*C*.
>
>
>
> Since *Z0* = sqrt(*L/C*), to keep* Z0* as a constant, the stripe line need
> to adjust it?s current distribution to maintain a constant *L*.
>
>
>
> Considering the loop area decrease because *h* is reduced, the current
> distribution should be more tighter to maintain a constant *L*.
>
>
>
> Finally the tighter current distribution on the returning pass results in
> the reduction of the cross talk.
>
>
>
> Are these correct? I will appreciate your help
>
>
>
> Best Regards
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
