[SI-LIST] Re: Problems with high speed link

Those are important things to look at.  That's not a recipe for success.


Steve.
Chen Jikai wrote:
> Hi,
> I have some thoughts about the limits to high speed links. Since I currently 
> don't have industrial experience in this field, could someone comments on 
> them with his/her industrial insights? Thanks!
>
> >From the SI books and papers, I understand that dielectric loss dominates 
> >the transmission line loss over skin effect loss at high frequencies. If we 
> >define FC as the frequency where the two loss mechanisms equal, then for 
> >conventional FR4 board, FC should be around 1G, which means for high speed 
> >link >10Gb/s, dielectric loss is dominant on FR4 boards. But if more 
> >expensive materials such as Rogers are used, this FC will be tens of GHz. 
> >Does this mean that for <50Gb/s links, if high performance materials are 
> >used, the optimization should be to minimize the skin effect loss? And once 
> >the loss tangent is below for example 0.002, it doesn't help much to reduce 
> >it even further. Is that true?
>
> Or for links <50G, neither skin effect loss nor dielectric loss is dominant. 
> Instead, the vias, connectors and packages will be the major bottlenecks. So 
> the emphasis should rather be put on 3D optimization of those transitions.
>
>
>       
>
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