How much does the impendence matter?

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presto

Joined: 26 Nov 2001
Posts: 39

23 Aug 2005 18:49 How much does the impendence matter?

Hi, there,

I'm going to design an adaptor board connecting a SFP fibre transceiver (2.5Gb) to a SMA or SATA type connector. Since the trace of 2.5Gb signal will be under 1 inch, I wonder if the impendence of the 4-layer PCB still needs to be carefully matched or general fabrication should be fine?

Many thanks

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flatulent

Joined: 19 Jul 2002
Posts: 4875
Helped: 324
Location: Middle Earth

23 Aug 2005 20:21 Re: How much does the impendence matter?

This is a significant fraction of a wavelength so you should consider it. Your biggest problems will be the transitions to the connectors on the ends. The manufacturers of the parts probably have application notes on how to shape the traces at the transitions.

spikeyang

Joined: 03 Mar 2005
Posts: 100
Helped: 5
Location: Shanghai China

28 Sep 2005 12:51 How much does the impendence matter?

Just use 50 Ohm microstrip line to the SMA connectort. It will not be much insertion loss.
Make sure what the width of your copper microstrip line. Avoid via hole s, iwhi
which will make impedance change.