[SI-LIST] Re: differential line

Zhangkun,

I have performed a study of exactly the same thing using HFSS
as part of a high speed board design seminar in 2001. You may
download the paper from the Ansoft website: http://www.ansoft.com 
Click on Events/Training and then (on the right) Archived Events.
Go to the bottom of the page and click on the "Ride the Wave"
event. Now look for the paper "Creating High Performance, 
Cost-Effective PCBs " In it you will see an analysis of a
diff pair over a slot in a ground plane.  The S21 is improved
when the traces are moved closer together.



Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel:  303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.grasso@xxxxxxxxxxxx;  
Email Alternate: chasgrasso@xxxxxxxx
 


-----Original Message-----
From: Istvan NOVAK [mailto:istvan.novak@xxxxxxxxxxxxxxxx] 
Sent: Monday, December 29, 2003 8:38 AM
To: zhang_kun@xxxxxxxxxx; si-list
Subject: [SI-LIST] Re: differential line


Zhangkun,

If the perforation holes are not much bigger than the trace width, and you
have a uniform pattern of small holes, no large cut or split, the
implications are: impedance goes up, crosstalk goes up. It is true that the
increase of crosstalk is usually more pronounced than the mismatch.  There
were several papers in the past showing the increased EMI radiation from
slots, and some also offered condensed equivalent circuits.  Let me know if
you need a short list of papers.

Regards,

Istvan Novak
SUN Microsystems


----- Original Message -----
From: "Zhangkun" <zhang_kun@xxxxxxxxxx>
To: "si-list" <si-list@xxxxxxxxxxxxx>
Sent: Monday, December 29, 2003 7:47 AM
Subject: [SI-LIST] differential line


> Dear All:
> Have anybody studied differential line or single line across 
> perforated
reference plane? I use Ansoft to analyze this problem. I find, when there is
a slot in the reference plane but and the reference plane is not cut, the
S21 is not affectted seriously comparing with the S21 when the reference
plane is integral.
>
> Could you give me some advice?
>
> Best Regards
>
> Zhangkun
> 2003.12.29
>
>
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