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Subject: Re: EMC on PCBs ???
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Date: 08/15/00 at 3:22 AM
Posted by: Jens Flucke
In Reply to: Re: EMC on PCBs ??? posted by tom stupfel on 08/09/00 at 5:32 PM:
thanks for answering my posting. I located the source. It is a 5 Gbit/s high speed line on serveral layers.
The Problem with the caps is that a "normal" cap isnīt a cap at 5 GHz. But we dont want to use normal microstrip
layout (large area), we are using lumped elements. We are using 0402 devices. So it
makes the reduction very complicated. On the other hand we had made some field simulations of the PCB.
In the plot you can see the the VC and the GND-Plane of the PCB is a kind of a waveguide. Which is using the
first mode (common mode, i do not know the English expression). Also a lead has a inductance of 1 nH, that
is a resistance of 31 ohms. The other problem is that a inductance radiate his energie into the enviroment.
We reduced the rise and the fall time, but we have also to fit the requirerde performance for our customers.
If you have an idea, please give advise.
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