[SI-LIST] Re: [SI-LIST]: Design a shielded differential line



1. I would use a field solver, like Apsim RLGC or Ansoft.  
2. I would not use broadside, as you show.  I would use edge-coupled, instead, 
due 
    to manufacturing problems (difficult to maintain the geometry, therefore 
the Z). 
3. Reference:  "Transmission Line Design Handbook",  Brian Wadell.  See 
    sec. 4.6. 
4. A shielded pair would have contiguous reference copper around all 4 
    sides.  Your diagram doesn't show this. 
5. Not sure why you specify "minimum capacitance between the differential line 
    and the ground" since that's fairly well set by your choice of FR4 and W, 
    unless you're doing something exotic like minimizing electrical length or 
    maximizing phase velocity, which aren't of concern, I believe, in normal 
    digital interconnect. 



----- Original Message ----- 
From: "PRIEUR, Olivier" <Olivier.PRIEUR@xxxxxxxxxxxxxxxxx>
To: "si-list" <si-list@xxxxxxxxxxxxx>
Sent: Tuesday, May 28, 2002 7:15 AM
Subject: [SI-LIST] [SI-LIST]: Design a shielded differential line


> 
> Dear All,
> 
> I want to design a shielded differential line in a PCB. 
> Nominal characteristic impedance of the differential line is 70 to 85 ohms 
> The recherched struture is 
> ______________            GND
>        ___                  h1 
>        ___                  h 
> ______________    h1   GND
> I have the added constraints:
> minimum width W of trace is .216 mm 
> thickness h, h1 of dielectric is 0.1/0.2/0.3/0.4/0.5 
> substrate dielectric constant about 4.7 (FR4) 
> I look for h, h1 and W. 
> I want a minimum capacitance between the differential line and the ground. 
> Do you know a formula, an article about this topic?
> 
> Best regards,
> 
> ------------------------------------
> Olivier PRIEUR
> e-mail: olivier.prieur @astrium-space.com
> ------------------------------------
>  
> 
> 
> ------------------------------------------------------------------
> 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:
> http://www.freelists.org/webpage/si-list
> 
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> 
> List archives are viewable at:     
> http://www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages 
> 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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages 
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: