[SI-LIST] Re: Floating Cable Shield
- From: Ivor Bowden <ivorlist@xxxxxxxxxxx>
- To: Moustapha Abdi Hassan <mahassan@xxxxxxxxxxxx>
- Date: Thu, 12 Oct 2006 10:24:16 -0700
Moustapha,
Thank you for sharing your experience. The "Cho-Jac" flat cable shield
product you linked at is interesting. I notice while they show shielding
effectiveness for the cases of drain wires only v.s. full enclosure,
they don't have any data on the floating case - but obviously it helped
for your situation. I wonder what the attenuation v.s. frequency graph
would look like in the floating case v.s. the other two they show, and
if it might increase crosstalk between signals on the cable.
Ivor
on 10/11/2006 9:18 AM PDT Moustapha Abdi Hassan wrote:
> We use this kind of shielding to improve the cable emissions. We did not
> have problem with FCC certification but we did have problem with a
> nearby pager which was too sensible and our product was causing the
> pager to go offhook. In our case just covering the cable with a metal
> shield (without any connection to ground) solved our problem.
>
> Here the link of the material used in our case :
>
> http://www.chomerics.com//products/documents/emicat/pg189chojacflatcable
> .pdf
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Ivor Bowden
> Sent: Wednesday, October 11, 2006 11:29 AM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Floating Cable Shield
>
> Hi,
>
> I ran into what I thought was an interesting cable and am looking for
> comments. This is an IDE cable on a new PC I got. The construction is
> twisted pair ribbon cable (flat spots for IDCs between the twisted
> sections), about 20" long, IDC both ends, a 3rd IDC about 7" from one
> end. What makes the cable interesting to me is there are two braided
> shields covering the bundled twisted pair sections, one about 8", the
> other about 3.5". These shields have no connections, not to a drain
> wire, not to each other and to to any circuit or frame ground, they are
> entirely floating. My question is, how effective is this type of
> "floating" shield, in terms of SI and EMI?
>
> This also brings up the general question of cable shield termination,
> circuit/chassis ground at both ends v.s. one end only v.s. floating;
> what characteristics to expect in each case?
>
> And that brings up the specific question of shield return treatment in
> the connector area, single drain wire v.s. complete enclosure?
>
> Thanks,
>
> Ivor Bowden
> Hardware Engineer
> Curtiss-Wright Controls Embedded Computing
> Video and Graphics
> San Diego, CA 92121
>
>
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