[SI-LIST] Re: Insertion Loss, Return Loss, ILD, UNi versus Dual stripline

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: "Haller, Robert" <rhaller@xxxxxxxxxxxxx>
  • Date: Thu, 05 Aug 2010 10:26:22 -0700

Robert, how fast do you want to go? The two things that will change will 
be:  distribution of conductor current, and dielectric loss.  If you are 
going 6Gbps or faster then dielectric effects are going to trump skin.  
Intuitively, I don't think Cu roughness and which side faces which plane 
is likely to be an issue unless you are trying to push 20Gbps or more.

The first case is going to have one core and one prepreg.  The second 
could be one of several geometries, but the best controlled will be:  
core prepreg core. If you have to use both:  core prepreg core, and 
prepreg core prepreg and you are going fast, then I think you have some 
work to do.  If you are only using core prepreg core, then I think for 
geometries within your ballpark other variations will be more 
significant than the symmetric versus offset stripline.  As always:  verify.

If you are trying to go fast, and/or are pushing your channel length, 
you might want to get help on your stack-up, and / or on design of a 
validation vehicle.  The last thing that you want to do is go through 
the time and expense of producing a test vehicle that doesn't properly 
characterize your channel as it will be manufactured.

Steve.

Haller, Robert wrote:
> I have 2 Diff pairs in the same dielectric Material (ISO370HR). One is Uni 
> Stripline, One is Dual Stripline. Aside from the potentially different 
> core/Prepreg material, resin content, glass weave (etc), and they are the 
> Same Copper Geometry (say 4 mil line/7 mil space) and have the same 
> impedance, same DC resistance  will I be able to observe a difference in 
> Insertion Loss, Return Loss, or Insertion Loss Deviation ?
> GND ---------------                    GND --------------
> Sig        -  -                                     SIG      -  -
> GND ----------------                   SIG                -  -
>                                                         GND ---------------
>
>
> Regards
> Bob
>
> Robert Haller
> Architect Engineer, Switching
> Enterasys Networks
>
> Phone: +1 978 684 1340
> Fax:     +1 978 684 1499
> E-mail:  rhaller@xxxxxxxxxxxxx<mailto:gnigg@xxxxxxxxxxxxx>
> Web:     www.enterasys.com<http://www.enterasys.com/>
>
>
>
>
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Steve Weir
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