[SI-LIST] Re: Routing 10G differential lines over Standard FR-4
- From: "Hassan O. Ali" <hassan@xxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 16 May 2005 10:38:46 -0400 (EDT)
On May 16, Bill Wurst <billw@xxxxxxxxxxx> wrote:
>
> Sunil,
>
> Unfortunately, there are no simple answers at 10Gbps. At that speed,
> there are three main concerns and you have already mentioned two:
> dielectric losses and discontinuities. The third is skin-effect losses,
> which can be mitigated by widening your traces and spaces and increasing
> the dielectric thickness to maintain a 100-Ohm differential impedance.
>
And there is one more concern: EMI.
At 10Gbps, microstrip lines don't need to be too long (in FR4, quarter-wave
length is
less than 8mm) to be perfect antennas to cause radiation loss and
electromagnetic
interference (EMI). If you're designing a product that is subject to
electromagnetic
compatibility (EMC) regulations, then you have to pay due attention to all EMI
sources.
Best regards.
Hassan.
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