FreeLists / si-list / [SI-LIST] Re: Silly question

[Ray Anderson <reanderson@xxxxxxxxxxxxx>]

Also, neglecting to ground the added 'dummy' plane and allowing it to 
float can create a mechanism to radiate EMI from (not unlike a patch 
antenna). From what you have told us, there is no reason to not ground it.

-Ray


eturkk  wrote:

>> <>On my home project front-panel I/O board, I initially had 1394 and
>> usb2.0 differential pairs going from connector to connector on a
>> _single_ layer board. The signals come from the pc motherboard with
>> a cable, and on this i/o board I connect them to appropriate
>> connectors.
>>
>> After learning the impedance requirements must be met, I ended up
>> adding a dummy plane so that the fab house can control the impedance.
>>
>> Do I have to connect that dummy plane to ground?
>

> <>Stuart Brorson wrote:
> <>Yes, you should connect the plane to GND. Although diff-mode currents
> <>flowing on the plane will cancel each other out, common-mode currents
> <>still need the GND return..... 


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